At least six people are dead and many others injured after a charter bus ran off Interstate 40 and crashed into a bridge support in Arkansas.

The crash occurred at about 1 a.m. Friday. The passengers were allegedly migrant workers who were on their way from Michigan to Texas, according to CBS News.

State troopers said they received notice of the incident around 1 a.m. They rushed to the scene and diverted traffic to the city streets through North Little Rock but were able to open one of the westbound lanes by 3 a.m. The diversions caused traffic to be backed up for a few hours, but it was cleared up by daybreak once all the debris and the bus were towed away.

The University of Arkansas for Medical Sciences said it received three patients at its hospital, reported the Los Angeles Times. Two were reportedly treated and released, while a third was admitted in fair condition.

The identities of the driver, victims and other passengers are currently unknown. 

What prompted the incident is still unknown as well. The crash occurred near the intersection of I-40 and the U.S. 67-167, which is known for being difficult to navigate since it requires drivers to change lanes if they want to continue following the route numbers that brought them into the area. Drivers only have about a minute to decide on a route before executing, according to the Associated Press.

Additionally, weather might have played a role since the light rain and fog which was present at the time of the crash could have hampered the driver's vision.