The Windsor-Detroit Tunnel is scheduled to close early Sunday morning for the annual Detroit Free Press/Talmer Bank Marathon.

Organizers say the tunnel will close around 6 a.m. Sunday and should reopen around 10 a.m.

The event attracts thousands of runners who'll cross the ambassador bridge, run down Riverside Drive and return to Motown through the tunnel.

The Ambassador Bridge will remain open, but lanes will be restricted.

The course starts in downtown Detroit and is billed as a marathon which takes participants through two countries.