A general view of the site of the derailment of a train carrying hazardous waste in East Palestine, Ohio, U.S., February 23, 2023.
CNN  — 

A federal agency has issued a new advisory urging major freight rail companies “to take immediate safety measures to look at the performance of the protective coverings over the pressure relief valves,” a spokesperson for the Pipeline and Hazardous Materials Safety Administration said Thursday.

The advisory, which does not mandate the measures, came as federal investigators probe further into the February 3 train derailment in East Palestine, Ohio. Several cars from the Norfolk Southern train were carrying the highly combustible chemical vinyl chloride when they derailed. The fiery wreck has since sparked outrage and health concerns in the local community.

Pressure relief devices are designed to prevent pressure inside tank cars from building up and potentially causing an explosion.

After the train derailed, officials determined at least one train car containing vinyl chloride had malfunctioning safety valves, and authorities worried pressure buildup in that car could lead to a catastrophic explosion of the chemical – hurling toxic fumes and deadly shrapnel up to a mile away. Crews averted such an explosion by breaching cars containing vinyl chloride, draining the hazardous chemical into a trench and burning it off.

Several of the tank cars had aluminum coverings meant to protect the valves and relieve pressure from tank cars to prevent damage, according to the PHMSA – a branch of the US Department of Transportation.

“In this instance, the aluminum housing covers melted in the fire caused from the derailment,” a PHMSA spokesperson told CNN. “That’s why we are issuing this Safety Advisory … that requests all rail companies review their fleets to determine if they have aluminum protective coverings and consider actions including replacing these covers with steel that can withstand greater exposure to heat and fire.”

The advisory came as all seven major freight rail companies in the United States, including Norfolk Southern, confirmed their participation in a voluntary safety reporting program, according to a Thursday letter sent to Transportation Secretary Pete Buttigieg from Ian Jefferies, CEO of the Association of American Railroads.

CNN first reported the companies’ expected participation earlier Thursday, citing a Biden administration source.

The reporting program, known as the Confidential Close Call Reporting System, is a voluntary program that allows workers to report safety hazards. Buttigieg had asked the companies’ CEOs to join the system and gave them by the end of the week to inform him of their decision, saying the program protects workers “from reprisal when they come forward.”

“We are committed to continuing the 20-year trend of continuous safety improvements in the rail industry,” Jefferies wrote in his letter.

NTSB: Train venting devices may have not functioned

In an investigative update on the derailment published Thursday, the National Transportation Safety Board also said it was “looking closely” at aluminum protective covers used on three of the vinyl chloride tank cars that derailed.

Investigators believe the aluminum covers on some tank cars may have melted in the fire and dripped into some pressure relief devices, “possibly degrading their performance,” the agency said.

NTSB Chair Jennifer Homendy told CNN earlier Thursday addressing this issue would not have prevented the derailment.

The pressure relief valves from these cars will undergo further examination later this month, the NTSB said.

The agency, which has been probing what may have caused the derailment, has said it could issue urgent recommendations at any point during its investigation.

TIMELINE: Here’s what has happened since the derailment

Train operator expected at meeting tonight

Meanwhile, Norfolk Southern was expected at a public meeting with East Palestine residents Thursday evening.

The company, which has been ordered by the EPA to fully clean up the wreck, backed out of a town hall with local officials last month, citing threats against its employees.

The toxic wreck left an immense amount of contaminated soil and liquids at the crash site – hazardous waste that’s now being trucked out for disposal.

In addition to residents who reported health effects, crews involved in the clean-up have also reported symptoms, according to a letter on behalf of workers’ unions to Buttigieg and Ohio Gov. Mike DeWine. CNN has reached out to Norfolk Southern for comment on the letter.

So far, roughly 2.1 million gallons of liquid wastewater have been removed from East Palestine, the governor said in a Thursday news release, citing Ohio’s EPA. That waste has been shipped to sites in Ohio, Texas and Michigan to be “disposed of through deep well injection,” the release said.

And roughly 1,400 tons of solid waste have been removed from the derailment site and taken to sites in Ohio, Michigan and Indiana, according to the release.

Indiana Gov. Eric Holcomb said Thursday the state will contract a third-party company to test the waste coming to his state for “dangerous levels of dioxins.” That sampling is scheduled to begin Friday, the governor said.

Earlier in the week, Holcomb said he was stunned to learn the waste would be headed to Indiana.

Crews in East Palestine will also begin removing the train tracks at the site of the derailment to remove the waste, including contaminated soil, underneath.

That work could begin as early as Friday, EPA officials said during a Thursday evening town hall.

The process would involve removing one side of the tracks, digging out the contaminated soil, conducting sampling and then replacing the tracks, EPA response coordinator Mark Durno said.

The same would then be done on the other side of the tracks, Durno added.

EPA will require train operator to test for dioxins

Officials have repeatedly said ongoing tests of the air and municipal water in East Palestine show both are safe.

In his Thursday update, Ohio’s governor said the latest lab results continue to show “no detection of contaminants” tied to the derailment in the municipal water and results from private water system tests also show no harmful levels of contaminants.

More than 150 private systems have been sampled, he added.

But residents remain wary of what impacts the wreck could have on their health – and community – in the longterm.

The federal EPA said Thursday it will require Norfolk Southern to test directly for dioxins – a kind of environmental pollutant – in East Palestine. Dioxins are considered to have significant toxicity and can cause disease, according to the National Institute of Environmental Health Sciences.

“If dioxins are found at a level that poses any unacceptable risk to human health and the environment, EPA will direct the immediate cleanup of the area as needed,” the agency said in a news release.

“EPA will also continue sampling for ‘indicator chemicals,’ which based on test results to date, suggest a low probability for release of dioxin from this incident,” the release added.

Since the wreck, locals have reported health ailments – like nausea and rashes – they worry are connected to the chemicals released after the wreck.

A lingering fruity chemical smell is caused by residual butyl acrylate, Ohio EPA Director Anne Vogel told CNN Wednesday evening.

Butyl acrylate, which is among the materials the train was carrying, is used to make plastics and paint. It’s possible to inhale it, ingest it or absorb it through the skin. It irritates the eyes, skin and lungs and may cause shortness of breath, according to the National Institute for Occupational Safety and Health. Repeated exposure can lead to lung damage.

Vogel said the levels being detected in water sampling are much lower than the federal hazard level for the compound in drinking water and well below levels that would cause immediate health effects, but added she did not know whether there could be longterm health effects. A health study currently underway may be able to help shed light on that, she said.

CNN’s Nouran Salahieh, Gabe Cohen, Gregory Wallace, Rob Frehse, Edward-Isaac Dovere, Phil Mattingly, Celina Tebor, Brenda Goodman, Laura Dolan, Nicki Brown, Betsy Klein and Manu Raju contributed to this report.