NORTHBOROUGH, Mass. -- Fire crews responded to a five-alarm blaze that tore through a shopping plaza on Route 20 in Northborough early Tuesday.

The fire forced safety officials to close Route 20, also known as Main Street. The fire was at 243 W. Main Street. Motorists were advised to seek alternate routes.

Officials said a limousine driver noticed the flames coming through the roof of the plaza and called 911. The buildings were vacant when fire crews arrived.

"At approximately 2:50 a.m. this morning we received a call into our 911 center by a passing limousine driver reporting heavy fire coming through the roof. There was very heavy fire to the rear of the building. I would assume that there is going to be extensive fire and smoke damage throughout the building. We have had a partial collapse of the roof midsection. I believe we're well over 60 to 70 firefighters at this time," Northborough Fire Chief David Durgin said.

The Northborough Shopping Center houses five businesses, including a supermarket, a restaurant, a jeweler, gift shop and a television store.

One of the owners arrived at the plaza horrified by the damage.

"It's like a nightmare. You don't believe it's happening. It only happens to somebody else, never you. Never," gift shop owner Jane Teczar said.

There was no word on how the fire started.