ALMA, Colo. (AP) - The U.S. Forest Service has stopped issuing access permits to hikers hoping to reach the top of four 14,000-foot peaks in Colorado because the trails cross private land.

The agency this week began distributing fliers warning hikers to keep off trails to Mount Democrat, Mount Lincoln, Mount Bross and Mount Cameron in Park County unless they have permission from landowners who acquired the land through old mining claims.

"The bottom line is there is no public access to those peaks," Sara Mayben, head of the Forest Service's South Park Ranger District, told The Denver Post. "We can't stop the public from trespassing, but we will take steps to make it clear that they are."

Interest in Colorado's "fourteeners" has soared in recent years, with roughly half a million people climbing at least one each year. The four peaks' proximity to Denver and their relatively low skill level have made them among the most popular of the state's 54 mountains taller than 14,000 feet.

Terri Gifford drove from Illinois to climb the four peaks in the Mosquito Range. She was surprised to learn they were off-limits.

"Are we not supposed to be up there?" Gifford asked as she rummaged for a map in her van at a trailhead. "It's in all the guidebooks."

Maury Reiber, one of the landowners in the area, said he's concerned he will face lawsuits if someone falls into one of the mine shafts that dot the slopes.

"We're trying to keep an open mind about different solutions, but these issues need to be addressed," Reiber said. "If we have to be hard-nosed and say `no one goes up there,' that's the way it's got to be."

Local officials have formed the Mosquito Range Heritage Initiative, which among other goals is seeking to work out access agreements with land owners.

"We have a compelling economic interest in seeing that these peaks remain open," said Richard Hamilton, a former county planner.

Access to at least two other fourteeners - Culebra Peak in the Sangre de Cristos and Wilson Peak near Telluride - is at issue because of the 1872 Mining Act, a Civil War-era law meant to develop the mineral wealth of the Western States, said T.J. Rapoport, executive director of the Fourteeners Initiative. The original claims were patented, meaning they were transferred to private ownership.