Firefighters worked Monday and Tuesday to manage a wildfire north of Arboles in southwest Archuleta County, allowing it to increase in size to 742 acres to remove fuels and improve forest health.

The lightning-caused Pine Tree Fire started Thursday and was expanded by firefighters over the last two days across Southern Ute land to clear out dead wood and materials left behind by forest thinning, said Pam Wilson, spokeswoman with the Durango Interagency Type 3 team managing the fire. The fire burned on an uninhabited area and did not threaten homes or infrastructure, she said.

Crews finished expanding the fire Tuesday and plan to monitor it for the next few days, she said.

The low-intensity fire did not burn all 742 acres, but that is the outside perimeter of the burned area, she said.

The fire left patches of green forest that will provide cover for wildlife and diversity in the forest, she said.

“We are pleased with how things went,” she said.

The fire grew to 530 acres Monday with help from a helicopter crew that dropped fire ignition devices from the air to spread the fire within a predetermined boundary. Ground crews worked to spread the fire Tuesday using drip torches and pingpong-like balls injected with glycol and potassium permanganate to light the unburned areas, she said.

The managed fire was responsible for smoke visible Monday and Tuesday from Buck Highway (County Road 521) and the U.S. Highway 160 and Colorado Highway 151 corridors, according to a news release.

Five people initially assessed the fire, and the crew working on it grew to about 80 on Monday, including two hand crews of 20 people each, a helicopter and several engines, according to the release.

Most firefighters will leave Wednesday, and the Type 3 team managing the fire will turn the fire over to a Los Pinos Fire Protection District commander Thursday, Wilson said.

Monsoonal rains may be coming into the area later this week, which could help extinguish the fire, Wilson said.

The fire is not expected to lead to problems with flooding because it was a low-intensity burn, and there are still materials in place to hold the topsoil in place, Wilson said.

mshinn@durangoherald.com

This story was updated to correct the county where the Pine Tree Fire is burning. The fire is close to the La Plata County line, but it is in Archuleta County.