The Metro-North train that crashed into an SUV in the Westchester County town of Valhalla Tuesday evening was traveling below the speed limit, officials said.

Sen. Chuck Schumer, a Democrat from New York, said preliminary indications are that the train was going 58 mph in a 60-to-70 mph zone.

What remained inexplicable was why the SUV driver found herself between the crossing gates as the train approached from the south. The collision killed her and five passengers in the first train car, according to officials. Fifteen others were injured.

Listen here to a passenger, Tom Mulligan, recounting his experience on the train:

A team of investigators from the National Transportation Safety Board arrived on the scene Wednesday morning and were expected to give a briefing at 5 p.m. at a nearby hotel.

Board member Robert Sumwalt said they would question witnesses and crew members and review the contents of the recorders from the train, crossing equipment and nearby traffic signals. 

"Those recorders have been secured and we will be looking at that today," Sumwalt told reporters shortly after arriving at the Commerce Street crash site.

Meanwhile officials were using dental records to identify the badly burned victims. Several others remained hospitalized, at least two with critical or serious injuries.

According to Metro-North spokeswoman Marjorie Anders, a black Mercedes was driving over the tracks when the crossing gate came down on it.

"The driver got out to look at the rear of the car," Anders said in an e-mail. "Then she got back in and drove forward and was struck."

The train then shoved the car about 10 train car lengths north. The car and the front of the train caught fire.

Hundreds of passengers moved to the rear of the train. One passenger in a rear car, Tom Mulligan, said he and his neighbors remained on the train for several minutes, unaware of how severe the accident was until a train official came down the aisle and them to evacuate.

"People punched those plastic emergency windows and pulled levers to open the doors on an emergency basis," he told WNYC in an interview. "And then you basically jumped out of the train about four feet down to the tracks and slogged through the snow to get around."

The crash occurred at around 6:30 p.m. The Harlem Line train was running express and had left Grand Central Terminal at 5:44 p.m. Westchester County Executive Rob Astorino said the train was full with as many as 650 people on board. An eyewitness who said he was in the car behind the SUV, Rick Hope, said traffic was moving slowly at the time because cars had taken side streets like Commerce Street in order to avoid the Taconic Parkway, where another accident had happened a short time earlier.

"It looks like she stopped where she stopped because she didn't want to go on the tracks," Hope told Fox 5 New York. "It was dark, so maybe she didn't know she was in front of the gate."

A video posted on the website of the Journal News, a suburban newspaper, showed smoke pouring out of the broken windows of a rail car, while emergency responders stood nearby.

Officials said the electrified third rail penetrated the vehicle and the train's first car, causing them to burst into flames.

It was the deadliest accident in the 22-year history of one of the nation's busiest commuter railroads — one that has come under a harsh spotlight over a series of accidents in recent years. New York Gov. Andrew Cuomo said the tragedy could have been much worse.

"When you look at the damage done and the damage by the fire, it's actually amazing that not more people were hurt on that train," he said.

Astorino said the train's engineer and conductors escaped after trying to help passengers evacuate.

Service on Metro-North's Harlem Line will remain suspended Wednesday between North White Plains Station and Pleasantville and replaced with shuttle buses, according to the MTA, and delays and crowding should be expected. The agency said tickets will be honored on the Hudson and New Haven lines, and that free parking is available at Cortland Station on the Hudson Line. In addition, the MTA announced the following plans for the remainder of the day and the afternoon rush-hour:

Northbound Service

• Trains are operating from New York City to North White Plains Station with shuttle bus service to Pleasantville. 
• Train service is also available north from Pleasantville to Southeast with connections to Wassaic.

Southbound Service

• Trains are operating from Wassaic and Southeast to Pleasantville.
• Shuttle buses are carrying passengers between Pleasntville and North White Plains, where service resumes to New York City.
• No service is available at the Hawthorne and Valhalla stations.

This is the second Metro-North crash with multiple fatalities in a little over a year. In December 2013, a train derailed in the Bronx, killing four and injuring scores. That crash brought renewed scrutiny to Metro-North from federal regulators, and the National Transportation Safety Board is investigating five incidents involving the railroad.

Metro-North is the nation's second-busiest railroad, after the Long Island Rail Road. It was formed in 1983 and serves about 280,000 riders a day in New York and Connecticut.

UPDATED 5 p.m. with more details about speed and identification of victims. UPDATED 1:15 with afternoon service changes. UPDATED 11:15 a.m.:An earlier version of the story, citing an official account, gave the incorrect make of the vehicle that was struck by the train. Other details about the evacuation and the NTSB investigation have also been added. UPDATED 8:15 a.m.: Officials said initially that seven people were killed. The article has been changed to reflect the revised count.

--with The Associated Press