The Dome Fire that has burned over 5,000 acres and caused the deaths of two pilots in Yosemite National Park was caused by an abandoned campfire, according to fire crews at the scene.

Investigators listed the fire’s cause on Inciweb, but did not release details on how they determined the cause. The fire’s latest update on Tuesday morning reported that containment is increasing while the fire’s growth continues to slow due to cooler temperatures and higher relative humidity.

“Crews were successful at tying in more of the fire perimeter to control lines along the north and northeast areas of the fire,” according to the latest update. “Firefighters continue to improve indirect and contingency lines ahead of the fire.”

Some incident personnel on Tuesday morning attended a procession in Modesto, California, for Ryan Cutter and Greg King, the two pilots who died in a helicopter crash while working the fire. The FAA’s initial incident notification said the helicopter, a Eurocopter AS32 Super Puma, crashed under unknown circumstances while on water bucket drops at the fire.

Personnel working the fire have attributed the increasing containment to several pack mules from the Shasta-Trinity National Forest delivering fire equipment and medical supplies to crews.

“These intelligent, strong animals provide invaluable support,” crews said. “Using pack mules allows helicopters to do other work, such as bucket drops; and mules can also be used in smoky conditions where a helicopter would not have good visibility to deliver supplies to a remote site.”

Read the Dome Fire’s Tuesday update here.