A three-alarm blaze burned for more than three hours at the Cupertino, Calif. Apple Inc campus until firefighters intervened and fully extinguished the fire.

According to the Santa Clara County Fire Department, they were notified about the thick smoke coming from 20605 Valley Green Drive at about 10:00 p.m. The fire rescue authorities deployed at least 60 firefighters at Apple’s headquarters to deal with the situation.

Firefighters from neighboring San Jose Fire Department were also sent to help. The smoke was visible in the area and fire rescue units from Santa Clara County, San Jose, Saratoga and Los Altos rushed to the scene to intervene.

The Santa Clara County Fire Department said that the blaze scorched the roof and the second level of the edifice known as Valley Green Six, one of the most recognized buildings in Apple campus. Valley Green Six provides accommodation for several hardware-based research and development projects currently in progress by Apple.

The fire most likely started under an air conditioning unit on the building’s second floor. Maintenance crews had worked on the air conditioning installation earlier that day, said deputy chief for Santa Clara County Fire Hal Rooney.

After it charred the roof and parts of the second floor, the blaze was contained and fully extinguished by fire rescue crews at about 12:30 a.m. early Wednesday morning.

"We got a good knock down on the fire. We're trying to evacuate the smoke now," said Rooney late Tuesday night.

Although the blaze wasn’t a very big one, the smoke from it may have caused a lot of damage, a Fire Department dispatcher told The Associated Press.

Fortunately, there were no injuries.