ALBUQUERQUE, N.M. (AP) — A fast-growing wildfire sparked by the fatal crash of a small medical plane outside Ruidoso, New Mexico, has triggered evacuations for a rural area north of the Capitan Mountains and closures in the Lincoln National Forest, officials said Monday.

The plane was en route from Roswell Air Center to Sierra Blanca Regional Airport when it crashed before dawn Thursday, killing the four people aboard. They were identified as pilots Keelan Clark and Ali Kawsara with the company Generation Jets and flight nurses Jamie Novick and Sarah Clark with Trans Aero MedEvac.

“Our hearts remain with the families and loved ones navigating an unimaginable loss,” Matt Goertz, vice president of Trans Aero MedEvac, said in a joint statement with Generation Jets.

The Federal Aviation Administration and the National Transportation Safety Board are investigating the crash.

The wildfire grew rapidly over the weekend amid dry and windy conditions, nearly doubling in size between Sunday and Monday morning to more than 19 square miles (50 square kilometers). It was burning out of control in a sparsely populated area despite the efforts of more than 600 firefighters from the U.S. Forest Service, the Bureau of Land Management and several interagency Hotshot crews.

Adam Turner, a public information officer for the fire, said steep, rugged terrain has made it impossible for crews to engage the fire directly.

“This is what firefighters call ‘mountain goat territory,’” said Turner, adding that crews were instead working to contain and steer the fire away from several evacuated cattle ranches to the northeast and the community of Arabella to the west.

A red flag warning remained in effect across southern New Mexico on Monday, with wind speeds forecast between 20-30 mph (32-50 kph).