A fire of unknown origin broke out today in Apple’s command center in Mesa, Arizona.

Local firefighters responded at around 11:30 Tuesday morning to the structure, which formerly held sapphire glass supplier GT Advanced Technologies.

A Mesa fire spokesperson said the flames seemed to be localized to the roof of the building, near Signal Butte Road and Elliot Road.

The building, originally built in late 2013, is now assumed to be a new “command center” for Apple, which just hired 500 extra workers for the facility.

Apple had to repurpose the address last October when the sapphire glass vendor GTAT filed for Chapter 11 bankruptcy after its failure to meet performance requirements kept the company from receiving its final $139 million payment from Apple and forced GTAT to lay off more than 650 employees.

No word yet as to the origin of the blaze; we will continue to keep an eye on the developments in this story.

Source: AZ Central