A multivehicle crash on I-75 involving an Atlanta officer caused a traffic backup Thursday morning that stretched into Clayton County as police investigated.

The northbound lanes were closed before Cleveland Avenue, just south of the Polar Rock neighborhood, at about 9:30 a.m., and two right lanes reopened 15 minutes later. Gridlock conditions stretched back to I-285 until the investigation was moved to a right shoulder at about 11:15 a.m.

The incident began when an Atlanta officer from the motorcycle unit tried to perform a traffic stop on a Chevrolet Impala that was traveling in the HOV lane, according to the Georgia State Patrol. Instead of pulling over to the right shoulder, the Impala driver reduced speed and began to stop on the left shoulder, which had a concrete median barrier and was not wide enough for the entire car to fit and move out of traffic. As a result, the officer had to stop the motorcycle in a regular travel lane.

When traffic began to slow behind the stop, the driver of a GMC Hummer that was in the HOV lane moved into a travel lane to get around and didn’t see the officer until the last second, according to the GSP. The Hummer driver tried to veer back into the HOV lane to avoid hitting the officer, but the vehicle’s front right tire and hood struck the front left crash bar of the motorcycle, throwing the officer from the vehicle.

Another crash happened when a Toyota Tacoma rear-ended the Impala. A Chevrolet Tahoe then rear-ended the Tacoma.

The officer and a passenger in the Tahoe were injured and taken to Grady Memorial Hospital.

A police spokesperson described the officer as alert. An update on his condition was not provided Thursday afternoon, and no further information was provided about the nature of the injuries.