HAZ-MAT SPILL: Crews work to clear highway after multi-vehicle collision on Fred Hartman Bridge

A multi-vehicle collision has closed down main lanes headed northbound on SH-146 on the Fred Hartman Bridge.

According to Houston Transtar, the accident involved a heavy truck that was carrying hazardous materials, however it is unclear exactly what caused the accident.

Traffic was reportedly backed up to the Spencer Highway exit.

Crews were still working to clear up the crash more than an hour after it occurred.

Officials are asking drivers to avoid the area.