Witnesses called Missouri State Highway Patrol, around 12:30 p.m. on Saturday, reporting that a commercial dump truck drove through the bridge railing on the highway and into Bee Creek.
"Our crash team is investigating to determine the cause of that, and the medical examiner's attempting to make positive identification of the deceased," said Sgt. John Dick.
The accident occurred just south of the Dearborn exit, slowing down northbound and southbound traffic for more than four hours.
"We've had them exit at Route E on northbound 29, and then they've been allowed to proceed either to 371 or the inner urban road Midwest of I-29 so they could continue north."
Sgt. Dick also said the driver was traveling north in the left lane before veering off into the creek.
Shortly after the accident, medical examiners removed the bodies of the driver and the passenger, who are believed to be from the Kansas City Metro area.
Troopers say the truck was carrying an unidentified load.
"I can't identify that substance. It appeared to be some type of road paving material," said Sgt. Dick.
The Missouri Department of Natural Resources cleaned the spill and the substance that went into the creek.
A tow truck used a crane to removed the vehicle.
Troopers are still investigating the cause of the accident, and will not release the name of the truck company or victims until it is complete.