The Forest Service is investigating a case of almost unbelievable vandalism. In Left Hand Canyon, just northwest of Boulder, at least 100 trees have been torn down in three different areas.

Many trees, some of which were 2 feet diameter and hundreds of years old, were pushed or pulled over, while others were snapped violently. Forest Service officials believe heavy machinery was used to carry out the mayhem around Labor Day.

The trees were apparently downed with the purpose of blocking the road, the Forest Service said. Deep trenches were also dug across the road, making it impassible except by scrambling on foot.

The crime could have a connection to an ongoing battle in the canyon, forest officials said. Some landowners whose property is near public roads and the Roosevelt National Forest are unhappy that people who hike, ride their motorbike or drive their off-road vehicles in the area may be trespassing. The damage is so severe that it could take years to repair.

"There's going to be a time lag of 100 or more years to try and get that value into the landscape," said Christine Walsh, with the Forest Service.

"This is somebody who purposely did not want anybody in their neighborhood," said off-roader Vernon Brandt.

Brandt, who drove his off-road vehicle over 2-foot-high boulders Thursday, said he believes property owners may have toppled the trees to try to get the Forest Service to close the area to people like him.

The Forest Service is trying to get landowners and off-roaders and others who use the area to get together. The aim is to come up with some kind of compromise so visitors have access and landowners don't have to worry about trespassers.

Walsh said she hasn't ruled out closing the area, but stressed investigators haven't reached any conclusions.

"Sometimes people just can't tell where the private property is, and sometimes users are just irresponsible," she said.