Arizona firefighters on Monday battled a blaze that destroyed three homes and chased residents out of a mobile home park, while crews in Colorado worked to halt a wildfire that threatened homes.

The southern Arizona fire, at Dudleyville about 30 miles northeast of Oracle, had covered only about 250 acres by late Sunday, said Judy Wood, a fire information officer for theArizona State Land Department (search).

However, it had destroyed three homes and 10 other buildings since starting earlier Sunday.

Wood said she didn't know how many people had been forced to evacuate the mobile home park in Dudleyville. Officials of the Pinal County Sheriff's Department didn't immediately respond to calls seeking comment Monday.

A blaze in southwestern Colorado had blackened an estimated 2,800 acres near Mesa Verde National Park (search), and was threatening nine homes, a commercial building and six outbuildings or other structures.

That fire, which started Thursday, was believed to have been caused by lightning. It was 20 percent contained Monday, fire officials said.

They were among 25 large wildfires active Monday in Alaska, Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, South Dakota, Utah and Wyoming, according to the National Interagency Coordination Center (search) in Boise, Idaho. So far this year, fires have charred 3.4 million acres, compared with 4.2 million in the same period last year, the center said.