LAS ANIMAS, Colo. (CBS4) — A brush fire that started east of the town of Las Animas Thursday has reached 1,432 acres in size, but residents of the nine homes previously evacuated were allowed to return Saturday morning.

The blaze did calm down overnight and was estimated at 50 percent containment Saturday morning. At sundown the day before, there was no containment.

Evacuations were lifted at approximately 9:30 a.m.

The fire ignited Thursday evening in the Purgatoire River bed two miles east of the Bent County Correctional Facility, but has burned east past that river’s confluence with the Arkansas River.

The Colorado Parks & Wildlife said the fire is approaching John Martin Reservoir State Wildlife Area and the Fort Lyon State Wildlife Area.

The fire is named the Black Bridge Fire because it started near a black bridge. No cause has been determined.

One evacuated resident, Bryan Simmons, told KKTV he transported his livestock to a neighbor’s property when the order was issued.

“In the 20 years we’ve been here, the river has been on fire four or five times,” Simmons explained, “so we’re familiar with the drill. It’s not an uncommon event to have fire on the river bottom down here.”

Bent County is under a Red Flag Warning. No outdoor fires of any sort are permitted.

Authorities are also wary that incoming thunderstorms Saturday could trigger an increase in fire activity.

The previously evacuated homes were in no more imminent danger, but “fire conditions could change and we could have to do this all over again,” said Bent County Emergency Manager Rick Stwalley.

Volunteers from the Hasty/McClave, Las Animas and Cheraw fire departments are spearheading the firefighting effort. Two Black Hawk helicopters from the Colorado Army National Guard is making bucket drops.