The Bull Draw Fire, burning in a remote area 12 miles northwest of Nucla, has grown to 26,370 acres, the Type 2 Blue Team said.
Containment was at 19 percent on Wednesday, compared with an estimated 12 percent on Sunday. The fire's estimated containment date is Sept. 15.
The fire is considered the top priority in the Rocky Mountain region, meaning that the team would be the first to receive new resources. About 388 personnel were working the fire as of Wednesday morning.
Light rain Tuesday in parts of the fire's footprint did little to slow the fire, and the storm's winds pushed the fire northwest and south. The fire grew 3,410 acres, spreading northwest in the Campbell Point/Coyote Basin and south into the 2004 Campbell Fire burn scar.
Engines and crews worked around homes in the Campbell area and built control lines that connected to the Campbell Fire scar.
On Wednesday, the fire grew 1,180 acres as it pushed north into Deep Canyon and threatened to spread on the canyon walls.
Engines continued mopping up scattered pockets of heat around homes at Campbell Point.
On the eastern flank of the fire, crews were felling hazard trees, thinning the forest edge and preparing for burnout operations later this week.
The Minnesota Incident Command System Type 2 Blue Team said the southern edge of the fire has two operations - one that uses hot shot and hand crews to build control lines on the fire's edge up to where it has stalled inside the 2004 Campbell Fire burn scar, and another that uses heavy equipment including bulldozers to build a second line of defense to prevent the fire from turning back toward homes and ranches in the Nucla area.
The western side of the fire was moving slowly toward natural fire barriers and was unstaffed.
On the northeastern edge, crews are felling hazard trees and preparing the Divide Road for burnout operations later in the week.
Incident commander Brian Pisarek has referred to the Bull Draw fire as a "long duration fire" that will continue to grow.
The fire was discovered on July 29 and was apparently caused by lightning.