FOXBORO -- A four-alarm fire Friday afternoon gutted an historic building at the former Foxboro State Hospital and sent five construction workers renovating it into condominiums scurrying for safety.

The fire in the third floor, attic and roof of a former patients' ward took nearly two hours to get under control with firefighters battling temperatures topping 90 degrees as well as the flames.

A Plainville firefighter suffered a heat-related injury while fighting the 12:30 p.m. blaze but his injury was described as not life-threatening.

The four-alarm fire was the first in Foxboro in a decade and sent 75 firefighters from 11 surrounding communities to help with the blaze.

The blaze was located in a brick building on Payson Road, built in 1891, and spread to the cupola and roof of an adjacent former ward building before it was extinguished. The cause of the blaze was ruled an accident but the exact nature of the cause was not immediately clear. No damage estimate was available.

The fire was the largest in Foxboro since the Ancyent Marinere hotel and restaurant on Mechanic Street was gutted on Feb. 21, 1997, Foxboro Fire Chief Gerald McNamara said.

The fire Friday was spotted by off-duty Foxboro fire Capt. Donald Treannie who was driving on Chestnut Street, which intersects with Payson Road.

Foxboro fire Capt. Treannie said he was visiting the new public safety building site when he spotted white smoke near the ward building.

However, he saw heavy black smoke, and fire coming from the roof, when he drove toward the building about 5 to 10 minutes later. He then radioed fire headquarters.

McNamara said firefighters initially focused firefighting efforts from outside the building because no one was inside and the structure was under renovation.

Firefighters shot water at the roof and the walls from ladder trucks and the grounds.

`` This was a completely exterior attack,'' McNamara said. `` There was no reason for risking firefighters' lives.''

Project Manager David Crocini said the five construction workers in the building made it out safely.

Building Commissioner William Casbarra said his office will analyze the incident. Casbarra said he believed the construction workers were removing material and doing asbestos abatements at the time of the fire. The building was otherwise empty.

Property owner VinCo Properties of Boston is planning a 70-condominium complex, known as Chestnut Green, as part of the reuse plan for the 93-acre state hospital land, Crocini said.

The 93-acre parcel is also eyed for 100,000 square feet of commercial space; 55,000 square feet of retail space; 73 single-family homes; and a new police and fire station.

A public hearing will be held at town hall on Tuesday to discuss VinCo's plans, said Jack Authelet, Foxboro's unofficial town historian.

Crocini said VinCo still plans to restore the ward to its historical appearance.

The property is listed on the National Historic Register, he said.

`` It's sad. We've grown to love these buildings over the past year. They're gorgeous. You can't construct anything like this today,'' Crocini said. `` We'll fix it.''

Resident Ellen Pillsbury hopes so.

`` This is the history of the town. People were residents here,'' she said while watching the firefighters.

`` The big thing is firefighter safety,'' Treannie said. `` We don't want to go in these.''

The heat from both the fire and the weather drained firefighters, who rehydrated themselves with bottled water and shade on the site.

`` It's 90 out today. You're probably talking 300 to 400 degrees,'' near the fire, Treannie said.

Spectators worried about the firefighters' safety as well.

Firefighters were from Mansfield, Norfolk, Norwood, Norton, Plainville, Canton, North Attleboro, Wrentham, Walpole and Sharon. Franklin firefighters manned the Foxboro fire station.

`` I'm here to watch, and make sure all the firefighters are safe, because I know them all,'' said resident Michelle Iagatta, whose husband Daniel was a call firefighter before being injured.

`` I know they've trained very hard for this, and they did a wonderful job of knocking it (the fire) down. They got it under control.''