A fire destroyed the two story mini-mall at 99 Mount Auburn St. yesterday morning, causing a half million dollars of damage, Cambridge Fire Department officials said yesterday.

It took 65 fire fighters, 16 firetrucks and almost two hours to control the blaze, which was apparently caused by an electric heater, said fire department Deputy Chief Gerald R. Reardon.

"The heater reached an ignition temperature and ignited some sort of combustible material around it," Reardon said.

At 3:46 a.m., a police cruiser called the fire department to report a three alarm fire, Reardon said. Within minutes, nine engine companies, five aerial ladder companies and one rescue company arrived on the scene.

Safety officers, division chiefs and support staff remained at 99 Mount Auburn St. until 9:00 a.m. yesterday, and investigators were there until late yesterday afternoon, department officials said.

Flames Engulfed Store

Onlooker Sean Bryan '93, one of the first witnesses to notice the fire, said he saw smoke while walking in the Square late that night, approached the scene, and watched as flames engulfed the stores.

"There was smoke coming out of the wall and itlooked like the building was about to collapse,"he said. "Then the wind started to pick up, thewindows shattered and the flames were shootingout. With the ventilation, the awnings and thewindow display caught on fire."

Firefighters arrived shortly after and beganbreaking in the remaining windows and the door,and used hoses to douse the flames, Bryan said.

"After the trucks arrived and started, itdidn't seem like it took that long to put the fireout," he said.

The mall, which lies between Tower Records andWordsworth Books, housed seven stores includingGnomon Copy, Little Russia, The Inside Corner, TheMillion Year Picnic-a comic book store, Woolcott &Co. the yarn store, Tumbleweed and Le FootSportif. The mall is now entirely boarded up, itsentrance roped off and surrounded by shatteredglass.

Late last night the remains of the mall'smerchandise could still be seen through blackenedwindows. The scattered remnants included charredsneakers, ruined posters and water damagedclothing.

Representatives from Gnomon Copy assessed thesite yesterday, said Jim Sutherland, president ofGnomon Copy, Inc.

"We have no specifics yet, but this willcertainly be devastating for the Gnomon Copyowner," Sutherland said.

Sutherland said the store was insured, but theowner may need assistance because much of hisequipment was damaged by the fire.

Gnomon franchise owners in the area are "tryingto rally support and to give him as much help aspossible," Sutherland said