Two people were killed and four more were injured after a dump truck crashed into several vehicles in the U.S. city of Houston on Friday, local media reported. The chain collision crash happened just before Friday noon at a toll plaza in west Houston, local media Khou reported. Police said a garbage truck, owned by a waste treatment company, struck an extended cab truck carrying four people, then crashed into a gold Honda with a deputy constable and his wife inside. The dump truck then slammed into a pickup truck that was stopped at the toll plaza, hit a concrete barrier and burst into flames, police said. The dump truck driver and the pickup truck driver both died at the scene. The deputy constable and his wife were transported to hospital in serious condition. Two of the four passengers in the extended cab truck were also taken to a hospital, police said. Their conditions and injuries were not known. The accident shut down a long lane, causing traffic to back up for miles. It's not clear what caused the dump truck to crash into other vehicles. Police have launched an investigation into the accident.