Two people were killed Sunday when a helicopter crashed while fighting the Dome fire in Yosemite National Park, officials said. The Eurocopter AS332 went down just before 3 p.m. during aerial firefighting operations, according to the Federal Aviation Administration (FAA). The National Transportation Safety Board (NTSB) and FAA have launched an investigation into the cause of the crash.

The identities of the two deceased have not been released. Aerospace company Precision, which operated the helicopter, confirmed the loss of two crew members in a social media statement. The company expressed profound grief and asked for privacy and compassion for the families and its team.

The Dome fire, which started on September 15 north of Wawona Dome in Yosemite, has burned more than 3,000 acres as of Monday. Firefighters reported the blaze was 15% contained. The difficult terrain, characterized by steep and rugged slopes, has made ground access challenging, putting greater reliance on water-dropping helicopters to combat the flames.

The helicopter involved in the crash was a twin-engine utility model built in 1994. It had been supporting firefighting efforts since the fire’s onset. Flight tracking data showed the aircraft was deployed over the fire starting at 9:38 a.m. Sunday.

At the time of the accident, the weather conditions included increasing cloud cover with light south to southwest winds of 3 to 4 miles per hour, according to the National Weather Service (NWS). Carlos Molina, a meteorologist with the NWS office in Hanford, said clouds were moving in from the southwest, with some at 12,000 feet and substantial cloud cover at approximately 25,000 feet.

Fire officials continue to manage containment efforts amid the challenging environment. The investigation by federal authorities will examine the circumstances surrounding the crash as the firefighting response proceeds.