A firefighting Sikorsky S64 helicopter with two individuals onboard crashed on Friday morning in central Utah, according to federal aviation authorities.

The US Forest Service initially declined to comment on the condition of the helicopter’s passengers, asking the public for “patience while we focus on response efforts” in a statement.

Emergency personnel are responding near Richfield, a city about 160 miles south of Salt Lake City, an agency spokesperson told the Guardian by email.

The exact circumstances surrounding the crash are unknown.

At a media briefing on Friday evening, Tyler Hecht, deputy incident commander with Great Basin incident management team, described the terrain as “very difficult”, and said rescuers “have not reached the scene of the accident” in part because the helicopter crash had started a new fire.

Asked about the morale of the firefighters battling to control the blaze, Hecht said it was “very somber with what’s going on. You know, they did take a tactical pause, regrouped, and they’re back fighting fire.”

The aircraft was in the vicinity of the Widemouth 2 fire, a blaze sparked by lightning that has raced through 105,000 acres since it began on 27 July. It is one of eight large fires burning across Utah, which cumulatively have swept through more than 331,000 acres, according to state data.

“Wildland firefighting is among the most dangerous jobs in the world,” Utah governor Spencer Cox wrote in a social media post. “Today is a painful reminder of the extraordinary risks these brave men and women accept to protect us.”

The Federal Aviation Administration (FAA) and the National Transportation Safety Board (NTSB) are investigating the crash.