- Investigators learn of repair work done in April to rail where head-on collision occurs
- In April, crews repaired a crack in a joint bar that connected two sections of rail
- Just before crash, a train engineer sees "an unusual condition on the track"
- NTSB sends sections of rail to a lab for further analysis
Maintenance work was recently performed on a rail where commuter trains collided head-on in Connecticut last week, investigators said on Friday.
One engineer saw "an unusual condition on the track" before his train derailed and was struck by a train traveling in the opposite direction on another track, the National Transportation Safety Board said.
The evening rush-hour Metro-North crash in Bridgeport injured more than 70 people.
Investigators have removed sections of the rail for further laboratory analysis on whether it factored in the accident, the board said in a statement on its investigation.
Inspection reports show that Metro-North railroad crews in April repaired a crack in a joint bar that was used to join two sections of rail together, the statement said.
"Metro-North is conducting an inspection and inventory of all the joint bars on its main line tracks," the board added.
The NTSB didn't provide further details on the unusual condition seen by the engineer of the eastbound train from New York to New Haven that it said "derailed, came to a stop, and was struck 20 seconds later by the westbound train" on May 17.
The investigation also indicates that the engineer of the westbound train applied the emergency brake before the collision. Both trains were traveling at about 70 mph immediately before the derailment and crash.
Technology to prevent collisions applies to operations on a single track and couldn't thwart the accident because the two trains in this case were traveling on separate, parallel tracks -- until the eastbound train derailed.