Seven months after a massive fire destroyed the SPS Technologies fastener manufacturing plant outside Philadelphia, the company revealed what started the February 17 fire and how they intend to rebuild it.

Company officials said the cause of the fire was an explosion inside a compressed air system, which was captured on video. They don’t know what caused the explosion and are waiting on the Fire Marshal’s Office to release their report on the investigation.

The new state-of-the-art facility, intended to be operational in 2028, will be approximately 350,000 sq ft, including office space. The complex will attain LEED certification – incorporating solar panels and other green features for enhanced resource conservation and ecological sustainability.

Operations at the facility will include environmental controls for the protection of air, water and soil. SPS’s team members will use the latest technology and automation to manufacture the industry leading fasteners used in aerospace and other industries worldwide.

The fire started after an explosion at the century-old factory. About 60 workers who were inside the 600,000 sq ft facility at the start of the four-alarm blaze escaped safely. A second explosion the next morning in a different section of the facility prompted a shelter-in-place order for residents within a 1-mile radius. Nearly 70 fire companies from the region responded to the fire, which took six days to fully extinguish.

SPS is owned by Berkshire Hathaway subsidiary Precision Castparts Corp., and has received numerous federal contracts from the U.S. Department of Defense.