CROWN KING, Ariz. — Playing with matches, being careless with a campfire, even burning a letter from an estranged husband: Some of the most devastating wildfires in the country's recent history have been started by people.

In Arizona, the latest human-caused wildfire has burned more than 15 square miles, destroyed four homes in the community of Crown King, forced a weeklong evacuation of more than 100 people and cost upward of $2 million to fight.

Despite fire restrictions, an aggressive public-awareness campaign and plenty of publicity about the effects of blazes caused by man, fire officials say people just aren't getting the message, and they're not sure they ever will.

"It's a little more depressing, or aggravating, when you know it's a human-caused start and it could have been prevented," said John Glenn, chief of fire operations for the federal Bureau of Land Management. "We're dealing with Mother Nature all the time and it's a given that we're going to have lightning starts, but that component that could be prevented. It's disturbing to a lot of people in the fire business."

People caused more than 73,000 wildfires that burned more than 5,300 square miles in 2007, according to the National Interagency Fire Center, based in Boise. That compares with about 12,200 lightning-caused blazes that burned about 9,100 square miles. Several Utah fires, but not the largest, were caused by humans last year, while the largest fire so far this year — a 1,400-acre blaze near Boulder, was probably ignited by people, although authorities haven't determined how it was started.

In an unusual event, more than 1,500 wildfires erupted in California after lightning strikes June 21 and have burned more than 800 square miles. But just like everywhere else in the country, most fires there are caused by man.

Lucas Woolf, lead investigator for the U.S. Forest Service in northern Arizona, said the majority of fires caused by people are the result of carelessness with camp fires.

Then there are those who say they did everything right and refuse to believe their actions led to a wildfire, Woolf said.

A fire that came within a half-mile of the historic Arizona mining town of Crown King began June 28 after a lost hiker started a fire either to signal for help or stay warm, said Yavapai County sheriff's spokesman Dwight D'Evelyn.

The steep, rugged area in the Bradshaw Mountains about 50 miles north of Phoenix is blanketed with timber that's either dead or bone dry from years of drought and bark beetle infestation.

"It was not smart because the conditions there are just devastatingly dry. ... It's just been a big barbecue," D'Evelyn said.

The Forest Service investigation continues, and no arrests have been made.

People who inadvertently start fires or set signal fires face up to six months in jail and a $5,000 fine and could be ordered to pay the costs of fighting the fire, Woolf said.

Crews protected most of the 400 homes and vacation cabins in and around Crown King. But other human-caused wildfires have been much more devastating.

In summer 2002, two separate blazes in eastern Arizona evolved into the worst wildfire in state history. One fire started as a signal fire, and the other was set by a firefighter seeking work. Together, the fires burned 732 square miles, destroyed 491 buildings and cost about $400 million to fight.

That same year in Colorado, a 215-square-mile fire destroyed 133 homes and one business and caused an estimated $29 million in damage. A former Forest Service employee said she accidentally started the blaze, despite a fire ban at the time, while burning a letter from her estranged husband.

Last October in north Los Angeles County, a 9-year-old boy admitted starting a blaze that ripped through 59 square miles and destroyed 21 homes. He had been playing with matches.

A month later, investigators say, five young men started an illegal campfire on state park land that turned into a wildfire that destroyed 50 homes in Malibu.

"As long as you've got people in the woods, you always have the risk," said Tony Sciacca, commander of the team fighting the fire near Crown King.