HOUSTON -- All southbound lanes of the Gulf Freeway, I-45, were blocked early Thursday due to a crash involving an HFD ambulance.

Police say officers responded to an alleged road rage incident on the freeway and set up barricades.

The ambulance was called to the scene to treat an injured person, and that's when someone went around the barricades and crashed into the ambulance.

Two firefighters were taken to the hospital by ambulance along with two other people. Another person with a broken femur was taken to the hospital by Life Flight.

No fatalities were reported.

All southbound lanes were blocked at Beltway 8, but the freeway has since reopened.

Map: View Houston traffic conditions.