(Bloomberg) -- The fiery rush-hour crash of a New York commutertrain in Westchester County that killed six people happened amid atraffic jam that sent a swarm of autos across a level crossing,said a union official representing the engineer.

The deadliest accident in Metro-North Railroad’s historyoccurred after an accident on the Taconic State Parkway, said TonyBottalico, general chairman of the Association of Commuter RailEmployees. Cars were diverted, crossing the tracks in the process.Gates came down atop a Jeep Cherokee, whose driver got out, gotback in, tried and failed to move foward, he said.

The train struck the trapped vehicle, killing the driver andtriggering an explosion and fire that left five dead on the trainas the electrified third rail of the track pierced the railcar andset it ablaze. Fifteen people were being treated in hospitals, withseven in very serious condition, Governor Andrew Cuomo said on CBStelevision.

“This was as gruesome as I have seen,” Cuomo said.

The crash, which the National Transportation Safety Board isinvestigating, came 14 months after a fatal Metro-North accident inthe Bronx, and presented a major obstruction on a transit arteryfor thousands of workers. On Wednesday, there will be no trainservice on the Harlem line between North White Plains andPleasantville, according to the Metropolitan TransportationAuthority, the state agency that operates the line.

Fatal Conflagration

The accident occurred at 6:30 p.m. Tuesday on a train scheduledto leave Grand Central Station at 5:44 p.m., according to MTAspokesman Aaron Donovan. It happened at Commerce Street inValhalla, about 28 miles (45 kilometers) north of MidtownManhattan.

The Jeep was driven about 400 feet by the hit, and gasoline inthe tank burst and ignited the first train car, Cuomo said. Theexplosion caused the electrified third rail of the track to come upand pierce the train, he said.

Bottalico wouldn’t name the engineer, whom he said has beenworking for Metro-North for three years and has been an engineerfor nine months. The engineer is an Air Force veteran and attemptedto rescue people from the train before he was overcome bysmoke.

“Military training really helped him in this situation,”Botallico said. “It’s a tragedy and everyone did the best theycan.”

Snarled System

The National Transportation Safety Board sent a team ofinvestigators to Westchester County early Wednesday. Board memberRobert Sumwalt told reporters before leaving Washington that theteam will be on scene for about a week, and determining a cause maytake as long as a year.

Trains between Pleasantville and North White Plains will remainsuspended “until further notice,” according to a statement postedon the Metro-North website. Limited service for buses and trainswill be available for Upper Harlem Line customers, it said.

There will be shuttle trains between Wassaic and Southeast withbus connections to Beacon Station on the Hudson Line for trainservice to Grand Central. There will be limited train service toGoldens Bridge with bus connections directly to North White PlainsStation for trains to Grand Central.

Spuyten Duyvil

In December 2013, a Metro-North train derailed near the SpuytenDuyvil station in the Bronx, killing four passengers and injuring63. The engineer in that fatal accident had a sleeping disorderthat wasn’t properly monitored, the NTSB said in October.

U.S. investigators said last year that Metro-North lacked“safety culture,” a deficiency similar to the causes of the 1986Chernobyl disaster, the 2003 Columbia space shuttle explosion andthe 2010 BP Plc oil spill.

Railroad management failed to investigate damaged tracks andfollow its own safety protocols, the NTSB said in a report releasedNov. 19. The agency examined five incidents that took place fromMay 2013 to March 2014, including the fatal crash in the Bronx.

The type of intersection where Tuesday’s accident occurred, aso-called grade crossing, has a bloody history.

Six people were killed and 16 were injured when atractor-trailer failed to stop at a grade crossing and hit anAmtrak passenger train in Miriam, Nevada, in 2011.

The accident prompted NTSB to call on the Federal RailroadAdministration and the Federal Highway Administration to develop aplan to help states improve safety. The administration said in aMay 1, 2013, letter to NTSB that it was still working on it.

The MTA is the largest U.S. mass-transit system. It serves anaverage 8.6 million riders per weekday on the New York City subwaysand buses as well as Metro-North and the Long Island Rail Road.

--With assistance from Alan Levin in Washington, DouglasLytle in London and Freeman Klopott in Albany.

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