BEND, Ore. -

A total of 18 one-way trail signs have been tampered with or vandalized over the past four months along or near the popular Phil's Trail mountain-biking area west of Bend, according to the Central Oregon Trail Alliance said Tuesday.

"This is the third round of vandalism we've found," said Woody Starr, chairman of the board for COTA.

It's not just confined to Phil's Trail. The Bend Trail, Phil's Canyon and Tyler's Traverse Trail all have reports of vandalism.

"We're not sure who is doing this or why, but it's kind of upsetting," Starr said.

COTA and the Deschutes National Forest have been partners since the signs were first implemented back in April.

"There's a lot better ways to provide us feedback that we are looking for, than tearing down signs," said Jean Nelson-Dean, a Forest Service spokeswoman.

At nearly $23 apiece, the signs cost COTA a pretty penny to replace. And already, volunteers have spent nearly 20 hours working to fix them.

Starr says he believes someone is just unhappy with the direction change.

"I can see folks saying, 'Well, I always rode it the other way.' But really, it affects less than seven miles of trail total," Starr said.

The crime is considered a federal offense. Whoever is responsible could face up to $5,000 in fines or up to six months behind bars for the damage.

"That's people putting their own time and money into making a great experience for someone else," Nelson-Dean said. "And to come along and just trash it, you're not doing anyone any good."

If you have any information about the vandalism, or want to give feedback about the signs, email COTA at directional@cotamtb.com or call the Deschutes National Forest at 541-383-5300.