Last Updated Nov 6, 2015 4:10 PM EST
LITTLE ROCK, Ark. -- A bus ferrying migrant workers from Michigan to Texas ran off a highway and hit a bridge in Arkansas on Friday, killing six people and injuring six others. The impact ripped off most of the bus' roof and ejected some passengers onto the interstate, but the driver survived.
The crash on Interstate 40 in North Little Rock happened at about 1 a.m., in light rain and fog following a heavy storm, but it wasn't immediately known if weather played a role. The National Transportation Safety Board is investigating, with an initial focus on the possibility of driver fatigue and on how the passengers were protected, spokesman Eric Weiss said.
Roberto Vasquez, 28, of Monroe, Michigan, was behind the wheel when the bus ran off the right side of the highway, struck a wall and then hit the bridge. Three of the six killed had been ejected from the bus and one was partially ejected. The other two died inside the bus, said Col. Bill Bryant, the head of the Arkansas State Police.
Officers were working with the Mexican consulate to notify the victims' families, Bryant added.
Vasquez has agreed to routine drug and alcohol tests, but there's no indication he was intoxicated, state police Maj. Mike Foster said.
Highway officials said the span remained structurally sound. Photographs from CBS Little Rock affiliate KTHV showed the bus with nearly all its roof torn off, with most of the damage toward the rear of the vehicle.
Traffic was snarled for hours, but the scene was cleared before daybreak.
Three employees of Vasquez Citrus and Hauling of Lake Placid, Florida, were transporting 19 workers from Monroe, Michigan, to Laredo, Texas. Police did not discuss the nature of their work, but the company had advertised for seasonal farmworkers last spring on a Michigan jobs site, saying the work would end in November.
A woman who answered the phone at the company Friday hung up as The Associated Press sought more information.
Immigration and Customs Enforcement officers were called in, but only to help local authorities communicate with the Spanish-speaking survivors, according to ICE spokesman Bryan Cox. He said his agency was not pursuing any kind of criminal investigation of the people involved.
Jeff Lawson, who owns Continental Charters in Detroit, told the Arkansas Democrat-Gazette that he sold a bus Saturday to a man who "said he needed a second bus to haul people from (Detroit) to Texas... and Florida." A "Continental" sign was still visible on the wrecked bus on Friday.
The American Red Cross was providing mental health services to those who escaped injury. "As you can imagine, people are pretty shaken by this," Regional Communications Director Brigette Williams said.