SCARBOROUGH — A three-alarm blaze has caused extensive damage to a commercial building in Scarborough that houses more than a dozen businesses.

Three firefighters were treated for heat exhaustion while battling the blaze at Scarborough Commons, which was reported at about 7:30 p.m. Monday.

The blaze in the building on U.S. Route 1 was under control by about 9:30 p.m., but the cause remains under investigation.

Crews from several surrounding communities help fight the fire, which forced the shutdown of a stretch of the highway.

The building housed several businesses, including law and medical offices, a yoga studio, and a hair salon.

There were reports that people were still working in the building when the fire broke out, but there were no reports of tenant injuries.

Thank you Cape Elizabeth, Buxton, Portland, Saco, Old Orchard, So Portland, Gorham, & Westbrook Fire for your help. pic.twitter.com/oIbSdRMQyP

— ScarboroughMaineFD (@ScarboroughFire) September 9, 2014

Scarborough crews returning from Saco, many crews still on scene on Us Route 1. This is a pic from the Saco Fire. pic.twitter.com/ImEKPiUsZl

— ScarboroughMaineFD (@ScarboroughFire) September 9, 2014

Another photo from the rear of the building at last nights fire. pic.twitter.com/thnfxKUsxe

— ScarboroughMaineFD (@ScarboroughFire) September 9, 2014