FALMOUTH — A collision between two cars in the northbound lane of Interstate 295 in Falmouth is causing a traffic backup that stretches for several miles into Portland.

The Maine State Police say a rear-end collision occurred around 4:20 p.m. when several cars swerved to avoid lumber that was strewn across the roadway.

Police are not certain why there was lumber on the two-lane section of highway. No injuries have been reported.