CHICAGO (CBS) — A semi rollover snarled traffic and prompted a hazmat response Wednesday morning on the Dan Ryan Expressway.

Around 2 a.m., a big rig truck apparently lost a wheel near the ramp from the local outbound lanes of the Dan Ryan to the Chicago Skyway. The truck crashed into the dividing wall, causing it to roll over.

Police said the driver was not injured.

The truck spilled diesel fuel onto the pavement, prompting the Chicago Fire Department to bring in hazardous materials crews to clean up. It took more than two hours for crews to secure the hazmat response.

The crash blocked the Skyway ramp while crews worked to tow away the truck. The wreck was hauled off the roadway by about 6:30 a.m., but the ramp was still blocked while crews wrapped up.