Investigators are searching for clues to why an SUV stopped on the tracks ahead of an oncoming commuter train, triggering a crash that killed six people on a major line outside New York.
They also hope to have answers soon to how fast the train was going, whether its brakes were applied and whether its horn was sounded as it approached the crossing.
Local officials yesterday worked to identify those killed in the deadliest accident on the country's second-busiest commuter railroad - one that has come under scrutiny after a series of accidents in recent years.
Fifteen people remain in hospital.
"Everybody wants to know exactly what happened so that if something can be corrected, we correct it," said Governor Andrew Cuomo.
Five train passengers and the SUV driver were killed in the crash in Valhalla, about 20 miles north of New York.
Authorities said the SUV driver got out of her vehicle momentarily after the crossing's safety gates came down around her. She then got back in and was trying to drive forward when she was hit.
The northbound Metro-North Railroad train left Grand Central Terminal in Manhattan at 5.45pm and hit the SUV about 45 minutes later.
The National Transportation Safety Board (NTSB) plans to examine the highway signals, rail signals and crossing arms.
Around 45,000 passengers take the Metro-North Railroad's Harlem Line on an average weekday, about 14,000 of whom board north of where the crash happened and would be directly affected by closures.
The electrified third rail pierced the Jeep and then tore through the floor of the first carriage of the train, sending billows of smoke into the air.
The crash is the latest in a string of accidents involving Metro-North trains in recent years.
One derailed near the northern edge of New York City on December 1, 2013, killing four people and injuring 70. It was traveling at nearly three times the speed limit for the section of track where it crashed.