A portion of the westbound Highway 401 is closed in Whitby after a collision.

A transport truck was involved in a crash leading to a diesel spill.

The westbound 401 is closed at Brock Street and the Consumers Drive on-ramp to the westbound 401 is also closed, but the OPP says drivers can re-enter the highway using the Brock Street on-ramp.

Clean up efforts are expected to take between four to six hours.