Police are investigating how two unmarked police cars collided at a busy intersection in Morley yesterday.

The vehicle crime unit cars, both Ford Falcons, crashed at the traffic light-controlled intersection of Benara Road and Tonkin Highway about 1.35pm.

The black Falcon was T-boned on its passenger side by the dark-blue Falcon. The collision forced the black Falcon on to the grass median strip and into a Benara Road sign.

It is understood the cars were travelling in opposite directions but it remains unclear in which direction they were headed.

A police spokesman said the cars were attached to a priority two task and were on their way to the incident when they crashed.

It is understood both cars had lights and sirens on at the time, as is permitted for a priority two task.

The drivers and their passengers were not injured. No other vehicles or property were damaged.

An independent police supervisor will investigate what caused the crash. Internal affairs investigators will be called to assist only if there is a breach of law or procedure.