A large team of lawyers from the state is investigating last month's spill and weighing whether to file civil or criminal charges, California Attorney General Kamala Harris said Thursday.
"We're going to go where the evidence takes us," Harris told reporters, saying she was working closely with Santa Barbara District Attorney Joyce Dudley's office to get to the bottom of what happened -- and why.
Preliminary findings from a government report released this week revealed that the pipeline was badly corroded before it ruptured.
Plains All American Pipeline, which runs the pipe, had discovered two weeks before the spill that the stretch had four troublesome spots, the report said.
The May 19 spill forced officials to close the popular Refugio State Beach in Santa Barbara while they assess and clean up the environmental damage.
"There's still quite a bit of work to do," said Richard Rozzelle, a district superintendent for California State Parks. He told reporters Thursday that the beach will remain closed until at least June 25.
More than two weeks after the spill, he said, dead birds and animals are still washing ashore.
'Extensive external corrosion'
Authorities haven't conclusively determined what caused the spill. But the preliminary report from the U.S. Department of Transportation said Plains All American Pipeline had found "extensive external corrosion" in the pipeline. In the worst spots, corrosion had eaten away 54% to 74% of the pipe wall, according to Plains' May 5 assessment.
Plains All American is among the worst violators of safety and maintenance regulations, according to a list by the U.S. Pipeline and Hazardous Materials Administration.
Plains surpassed all but four of more than 1,700 operators in safety and maintenance infractions, the federal agency said.
Plains spokesman Patrick Hodgins suggested the comparison wasn't fair because "we're also much larger than those companies that we were compared to." The others are about half his company's size, he said.
Plains has had 175 federal safety and maintenance violations since 2006
, responsible for more than 16,000 barrels of spills that have caused more than $23 million worth of property damage.
273,420 gallons in spills
Plains CEO Greg Armstrong has said he's deeply sorry for the spill.
"We apologize for the damage that has been done to the wildlife and to the environment, and we're very sorry for the disruption and inconvenience that it has caused the citizens and visitors of this area," he said.
The company has been committing money to safety improvements for the past seven years, said Pat Hutchins, the company's senior director of safety.
But Plains was ordered to pay more than $40 million by the Environmental Protection Agency and the Justice department back in 2010.
At the time, regulators found the company violated federal environmental regulations 10 times from 2004 to 2007, when about 273,420 gallons of crude oil were discharged into waters or shorelines in Texas, Louisiana, Oklahoma and Kansas, the Environmental Protection Agency said
Most of the spills were caused by pipe corrosion, the EPA said.