Lenexa ? A multivehicle traffic accident near Interstate 435 left three people dead Saturday, authorities said.

The accident appeared to have been triggered by a northbound vehicle crossing the grassy median and running head-on into southbound traffic. The accident happened about 11:30 a.m. near Kansas Highway 10, police said.

First responders called for additional rescue vehicles to help. At least one vehicle was engulfed in flames. The accident forced Kansas State Highway Patrol troopers to close the southbound lanes of I-435 and the two left lanes of northbound I-435.

Witnesses said 40 to 50 people stopped to help and used fire extinguishers to put out the flames. They helped pull at least one mother and a child from a vehicle.

The accident did major damage to at least four vehicles, and others may have suffered lesser damage.

Initial reports indicated that the wreck involved one passenger car, two minivans and one vehicle of undetermined nature.