A fire that destroyed a northwest Atlanta apartment complex and left hundreds displaced last weekend happened during an “unsanctioned” party on the building’s rooftop, officials announced Friday.

More than 100 people attended the party at the Bell Collier Village apartments in the 1900 block of Howell Mill Road on July 27. Fire officials confirmed the blaze, which began around 6:20 p.m., is suspected to have been ignited by a propane grill filled with charcoal, a violation of building safety protocols.

Over the span of two hours, 80 fire department personnel worked the scene, dispensing more than 250,000 gallons of water to extinguish the flames. Authorities said the blaze was fueled by a “combustible rooftop deck and unprotected roof membrane,” and that “property owners’ inadequate fire controls significantly contributed to the fire’s intensity.”

“The failure to maintain essential fire safety measures and the presence of an unsanctioned party with hazardous equipment underscores the need for property owners to ensure compliance with safety standards,” Atlanta fire Chief Roderick Smith said in a news release. “This disregard for fire regulations not only endangers lives but complicates our emergency response efforts.”

Bell Partners, the property management company, told The Atlanta Journal-Constitution they were aware of the fire department’s findings but did not provide any other specifics into the incident.

“Bell Partners takes the safety and security of our communities very seriously. We are in receipt of a statement issued today by the Atlanta Fire Rescue Department regarding a recent incident at Bell Collier Village in Atlanta. We continue to cooperate with all applicable authorities relating to this matter,” a spokesperson said.

Officials have not said if anyone is facing charges.

No residents were injured, and everyone, including pets, were evacuated from the 256-unit complex, authorities said. One fire department member experienced heat exhaustion and was treated on-site.

A similar fire was ignited in November at the Reserve at LaVista Walk. That blaze started when two people set off fireworks on the roof, causing parts of the complex to go up in flames and hundreds to be displaced.

Smith described that fire as “a complete anomaly” since it started on the roof. He added that the location might have impacted and delayed the alarm and sprinkler systems.