A passing motorhome sparked a string of small fires this afternoon along U.S. Highway 97 in the south end of Bend.

A failure in the motorhome’s exhaust system caused the fires, the Deschutes County Sheriff’s Office announced this evening. Burning material from the exhaust was blown to the highway shoulder, starting the fires. The driver of the motorhome cooperated with investigators and no charges have been filed.

The fires, five in all, sprang up shortly after 4:30 p.m., in brush along the east side of the highway between Baker and China Hat roads. Smoke from the fires caused the closure of the northbound lanes of the highway, as well as the Baker Road overpass, for about two hours. Traffic snarled as a detour wound highway traffic through part of Bend.

The largest of the fires burned 5 acres and the rest were under an acre, said Kassidy Kern, spokeswoman at Central Oregon Interagency Dispatch.

While close to homes, the fires didn’t prompt any evacuations, said Deschutes County Sheriff’s Lt. Scott Shelton. Smoke pouring over the highway posed the biggest threat, making it hard for drivers to see where they were going.

“There was a lot of chaos and lots of smoke,” he said.

As of 7 p.m. all lanes of Highway 97 passing through Bend were open, said Dave Thompson, spokesman with the Oregon Department of Transportation.