Here's what you need to know about the Highway 401 detour

The westbound lanes of Highway 401 remain closed between Mallorytown and Reynolds Roads after a massive 30-vehicle crash Tuesday that left one person dead.

In a tweet Wednesday evening, Ontario Provincial Police said the eastbound lanes reopened at the site of the crash. 

Police say the cleanup is expected to be "lengthy," and officials from Ontario's Ministry of the Environment are on scene assessing the toxic substance that spilled from a transport truck.

If you're heading west, you have a couple of options.

Heading west? Here are your 2 detours

If you're heading west, exit the highway at Mallorytown Road and head north until Highway 2. Then take Highway 2 west all the way to County Road 3, which is also called Reynolds Road. Head south on Reynolds Road until you reach the Highway 401 westbound ramp.

The second westbound option is to get off the 401 at Mallorytown Road and head south until you hit the Thousand Islands Parkway. Take the parkway until you reach Reynolds Road, which will take you back to westbound Highway 401.

Click on the tweet below to enlarge the detour map.

The OPP have not said when they expect the westbound lanes to reopen.