BILOXI, Miss. — The number of accidents at the same grade crossing prompted the National Transportation Safety Board to investigate a fatal accident in Biloxi, Miss., Board Member Robert Sumwalt tells news media.

Sumwalt is heading an NTSB investigation team that is looking into a collision on March 7 between a charter bus and a CSX train. Four people died and another 41 were taken to area hospitals. The bus was shuttling 49 people from a senior center in Bastrop, Texas, between casinos in Biloxi and Bay St. Louis, Miss.

The accident happened after the bus got caught on what Sumwalt called a “hump,” a high crown between street and track levels. The eastbound 52-car train was traveling at 25 miles per hour, the engineer applied emergency brakes about 500 feet before the crossing, slowing impact speed to 19 mph, Sumwalt said. The impact shoved the bus 200 feet.

There were 2,025 grade crossing accidents with 265 fatalities in 2016, and NTSB does not investigate all of them, Sumwalt says.

“What got our attention here was that there was another event two months ago, right here. So we're very interested in that,” Sumwalt said. In January a Pepsi delivery truck was struck by a train when it got stuck on the tracks. The driver was not injured.

All told, the crossing has been the site of 17 accidents since 1976, three of them fatal, Sumwalt says. Reporters asked if the NSTB would make recommendations on the crossing. Sumwalt declined to answer, but said the investigation would look at all aspects of the incident.