A fast-growing wildfire in southern New Mexico that officials linked to a fatal medical plane crash outside Ruidoso accelerated over the weekend, triggering evacuations for a rural area north of the Capitan Mountains and prompting 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 four people aboard, authorities said. Officials identified the pilots as Keelan Clark and Ali Kawsara with the company Generation Jets, and identified the flight nurses as Jamie Novick and Sarah Clark with Trans Aero MedEvac.

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

In the meantime, federal agencies including the Federal Aviation Administration and the National Transportation Safety Board began investigating the crash.

As the blaze spread, officials said conditions on the ground made direct suppression difficult. Adam Turner, a public information officer for the fire, said steep and rugged terrain limited crews’ ability to fight the flames directly, describing the area as “mountain goat territory,” and saying firefighters instead worked to contain and steer the fire away from evacuated cattle ranches to the northeast and the community of Arabella to the west.

Officials said the wildfire nearly doubled in size between Sunday and Monday morning, growing to more than 19 square miles (50 square kilometers). They said more than 600 firefighters from the U.S. Forest Service, the Bureau of Land Management, and interagency Hotshot crews worked to control the fire.

Despite the staffing and activity, officials said the wildfire remained out of control in a sparsely populated area. On Monday, a red flag warning stayed in effect across southern New Mexico, with forecasters predicting wind speeds between 20 and 30 mph (32 to 50 kph), a combination that can help spread wildfire quickly.

The crash and the wildfire response unfolded in parallel: federal investigators worked to determine what happened to the aircraft, while fire officials focused on protecting communities and ranches in difficult terrain as the fire expanded.