JACKSON, Miss. -- The Texas tour bus hit by a freight train in a deadly crash wasn’t supposed to have taken the road where it got stuck at a rail crossing earlier this week, a federal official said Thursday.

National Transportation Safety Board member Robert Sumwalt said the driver may have followed a GPS set for commercial vehicle use rather than directions from the tour company, CBS affiliate WLOX-TV reported.

Speaking at a news conference, Sumwalt also said two other buses apparently followed the route provided by Florida-based Diamond Tours to the casino where they were headed in Biloxi, Mississippi.

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All three buses were set to leave around the same time and travel to the casino Tuesday afternoon, WLOX-TV reported. Only one bus was operated by Echo Tours, and that was the bus involved in the fatal collision.

In Texas, survivors and family members of the dead began filing lawsuits as more details emerged of the crash, in which the CSX freight train slammed into the bus at a humped rail crossing on Biloxi’s Main Street.

The NTSB official Sumwalt said a forward-facing camera on the train took clear color photos of the bus leading up to and immediately after the crash, The Sun Herald reported. Sumwalt didn’t give details of what the pictures showed and said investigators haven’t yet interviewed the driver. He said the investigation is continuing and a team will be traveling to Dallas to meet with bus owner Echo Transportation, and to Florida to meet with Diamond Tours.

WATCH LIVE: National Transportation Safety Board update on investigation into deadly train/charter bus crash in Biloxi. Posted by WLOX-TV on Thursday, March 9, 2017

A survivor said Thursday that after the bus became lodged on the crossing, the bus driver yelled for all the passengers to get off shortly before the train hit. The female passenger was seated right behind the driver.

“He told us to get off, and he was trying to see that everybody got off,” said Justine Nygren, speaking by phone with The Associated Press after returning to her Texas home. “He stuck with the bus, I know that. He didn’t get off when we did.”

Nygren said she left through the front door of the bus and walked a short distance alongside the tracks, not looking back. As she did, the train struck the bus and pushed it past her, she said.

Another bus returned her and seven other uninjured survivors Wednesday night to Bastrop, Texas, the Austin American-Statesman reported. The weeklong trip was organized by a senior citizens’ center in Bastrop, about 30 miles east of Austin.

Among the lawsuits, Mitch Toups of Beaumont, Texas, sued CSX and Echo on Thursday in a Dallas County court on behalf of survivors Darwyn and Marie Hanna. Both were injured, according to the lawsuit. It doesn’t describe the injuries but said they probably will “endure physical pain, suffering, and mental anguish for ... the rest of their life.”

Attorney Mikal Watts said he filed suit Wednesday against the railroad, the bus company and its unidentified driver in state court in Dallas for Peggy Hoffman’s son. His lawsuit, like Toups’, requests at least $1 million in damages.

The two others killed were identified as Clinton Havran, 79, of Sealy, Texas, and Deborah Orr, 62, of Bastrop, Texas.

Sumwalt had said earlier that the crossing on Biloxi’s Main Street has a hump that has caused tractor-trailers to bottom out, and the federal agency is looking into whether the steep grade played a role in Tuesday’s crash.

A soft drink delivery truck and a tractor-trailer also were hit by trains after getting lodged at the same crossing in January of this year and August 2014, respectively.

Watts’ lawsuit said CSX Transportation allowed “ultra hazardous” conditions at the crossing, and that the Echo Transportation driver failed to follow traffic signs.

The crossing has a warning sign about low clearance, topped by a graphic of a tractor-trailer stuck on a railroad track.

“CSX was responsible,” Watts said. “Instead of fixing it they put up a sign warning that vehicles could get caught. The bus driver either didn’t see the sign or, if he did, went over anyway, resulting in the deaths of four good people and injuries to 25 or 30 others.”

CSX spokeswoman Laura Phelps and Echo spokesman John Ferrari said in separate emails that their companies don’t comment on pending litigation.

Phelps said Wednesday that the railroad can only work four to five feet out from its tracks on a public road, so creating a more gradual slope would be up to the city.

The crossing has had at least 17 accidents involving vehicles and trains since 1976, though 11 involved moving cars or trucks -- including one in which an automobile hit the 38th car of a train that had stopped on the crossing.

Two other wrecks involved cars which were “stalled or stuck” on tracks; neither report had any clarifying details.

Crossing collisions are happening more often all over the U.S., CBS News’ transportation correspondent Kris Van Cleave reported. Deaths at rail crossings nationwide had been on the decline until an uptick in 2014, when 264 died. They rose again last year.

Following a 2015 accident between a commuter train and a pickup in California, the NTSB called for GPS makers to warn drivers about the more than 200,000 street-level rail crossings in the U.S. One other issue: outdated or malfunctioning signals. That’s what led to a crash outside Dallas in 2007.

“There’s so much more that we can do,” said Sarah Feinberg, the Federal Railroad Administrator under former President Obama.

Last year, the federal government gave states nearly $400 million to improve safety at rail crossings. The Mississippi crossing where 17 accidents have occurred, including Tuesday’s, didn’t even make the government’s top list of most dangerous crossings.