Large plumes of smoke were visible as firefighters conducted burnout operations to remove fuel in the interior of the fire's boundaries.
''I think they have a pretty good handle on it,'' said Dan Ware, state Forestry Division spokesman. The fire remained 70 percent contained Monday evening, he said.
The fire _ tackled by 70 to 80 firefighters _ was burning salt cedar, Russian olive and cottonwood trees along with grass east of San Antonio.
Fire activity was minimal Monday because of low temperatures and light wind, Ware said.
The blaze began Saturday when a private landowner operating a grinder sent sparks into some grass. Strong wind churned the flames Sunday.
Firefighters had estimated the blaze at 1,200 acres, but Ware said better mapping caused the number to fall.
The fire was not threatening any structures, he said, but firefighters were standing by in case structure protection was needed.
The blaze is bordered on the north by an existing fire break on private land, to the south by U.S. 380 and bulldozer lines, to the west by the Rio Grande and to the east by a road.
