A crash involving a tractor-trailer and at least five other vehicles forced the closure of westbound lanes on Route 2 for hours starting Monday morning.

Massachusetts State Police troopers from the Athol Barracks responded to exit 79 on Route 2 at 9:53 a.m. Exit 79 is on the Phillipston/Templeton line.

The crash initially forced the closure of the highway in both directions, but eastbound lanes had reopened by just after noon. Lanes heading west were still closed as of about 1 p.m.

The collision caused serious injuries, WBZ Traffic reported.

No further information was immediately available.

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