A wildfire burning on part of a southern New Mexico ranch owned by veteran newsman Sam Donaldson is forcing residents to evacuate.

The fire nearly tripled in size over the past day to more than 43,000 acres Wednesday. It's burning in steep terrain.

Lincoln County sheriff's deputies and staff with the New Mexico Livestock Board are helping residents and their animals evacuate the Alamo Canyon area. Residents were advised the day before to be prepared to leave.

Crews are using bulldozers to cut fire lines and are conducting back-burns in an effort to rob fuel from the blaze.

They're getting help from several single-engine planes and a C130 air tanker.

The wildfire is believed to have been caused by lightning.