FORT TOTTEN - The eight tribal firefighters at the Spirit Lake Nation dread the time between snow melt and green up. That's when fields of dead prairie grass bring out the fire-starters.

"I'd say 75 percent of them are somebody lighting a fire to light a fire," Spirit Lake Fire Chief Daniel Herman said. "Why? I've been asking myself that for a long time."

The firefighters can respond to more than a dozen grass fires set each day from late March to early May, Herman said.

It's dangerous and exhausting work - made worse because most of the fires are senseless, leaving much of the 300-square-mile Sioux reservation near Devils Lake a patchwork of scorched earth, Herman said.

Other reservations share that problem, said Lyle Carlile, the Bureau of Indian Affairs' fire director at the National Interagency Fire Center in Boise, Idaho.

The BIA has established special Wildfire Prevention and Investigation teams to send to reservations with problems caused by purposely set fires. "Indian Country has a long history of emergency firefighters mobilized all over the country to fight fires," Carlile said. "We also have issues at home with human-cased fires that we're trying to address."

Last year, there were 8,034 fires on American Indian reservations and 6,561 of them were "human caused," the BIA said. Nearly 475,000 acres of reservation land was charred, more than half of it burned either by arsonists or fires that escaped control.

The Dakotas accounted for about a third of the intentionally set fires on American Indian reservations last year, the agency said.

On the Spirit Lake reservation, most of the fires are small fires, an acre or less, though one fire last year blackened about 1,300 acres, Herman said.

One fire last month that came within 100 yards of a home was a classic case of arson, investigators say. Starting from a clump of dead grass, the fire was pushed by strong winds and took off in a V-pattern across the prairie, scorching some 60 acres before firefighters had it doused.

While fire investigators can identify arson fires, finding whoever set them is difficult.

Carlile and the tribal fire chief say fire investigators on reservations help stop intentionally set fires through education and enforcement. A new hot line that pays tipsters to report arsonists also helps, they say.

A team was sent to the Spirit Lake reservation in late March at the urging of tribal officials.

"We looked at our average and felt that it was too high, so we asked the BIA to bring in a team," Herman said.

Colleen Reinke, a member of the fire prevention team hired by the BIA, said the 292 fires were reported on the reservation between late March and May 2. All but 20 were in April, she said.

"The first one we went to was surrounded by snow," Reinke said.

Most of the fires were intentionally set, either by arson from trash or a fire in a field that got out of control.

Reinke said it's too early to say if the investigators' presence on the reservation made a difference this year. But she said the investigators "did raise awareness that there is a problem."

Lee Schmunk, a BIA fire prevention specialist from Fort Meade, S.D., said investigation is a part of prevention.

Schmunk, who helped investigate fires on the Spirit Lake reservation in April, said the prairie grass there is "as flammable as gasoline."

Many of the fires on reservations are caused by children playing with matches or lighters, he said.

"Almost all young males are fascinated with fire," Schmunk said. "Unfortunately, girls are catching up. We're seeing more juvenile females who are fire-setters too."

Team members visited schools, educating children about the danger of fire. They also pushed for a permitting process for burning and saw a "tenfold increase" in burn permits this year, Reinke said.

Spirit Lake Chairwoman Myra Pearson said the fires have been going on as long as she can remember on the reservation.

"Every spring, everywhere you look there is smoke," Pearson said. "People are afraid to go to sleep at night. They don't burn year round, thank God."

The Spirit Lake tribe has 6,100 members and about 4,500 of them live on the reservation. Pearson said she can't remember any deaths caused by the fires over the years. She said tribal members have been lucky.

"This is a serious issue," Pearson said. "We need to get something done before something serious happens."

Pearson said prosecution is the key to quashing arson on the reservation.

Reinke said several of the fires were being investigated as arson but no charges had been filed.

The program first came to North Dakota two years ago, on the Turtle Mountain Indian Reservation, said Jim Hamley, a fire investigator for the BIA.

Hamley, who lives on the reservation, said several juveniles were referred to the courts as arson suspects after an investigation into grass fires.

"The fires have gone down from about 350 year, down to about 100," Hamley said. "It has made a difference and people are becoming more aware - but it's not going to change overnight. It's going to take time to reverse this."

Sam Scranton, the BIA's top fire prevention specialist in Boise, Idaho, said the agency has 17 BIA investigators and 140 others who are being trained.

Scranton said the agency has a $3.5 million budget for the program, which has sent fire investigators to California, Oklahoma, Arizona and South Dakota in recent years.

The agency has received about 400 tips a year reporting suspected arsonists, Scranton said. About $6,200 in tip awards was approved last year, and the agency already has approved about that much this year, he said.

Many rewards go unclaimed on the reservations, he said.

"Not everyone wants the reward," Scranton said. "They just want the problems stopped."