Bicyclists beware, or be aware there might be tacks on the I-90 bike trail, big enough to cause flat tires or worse.

Commander Dave Jokinen with the Mercer Island Police Department said the department was informed of the situation around Oct. 17.

Jokinen said the parks department has cleaned up the trail, and patrol units are on alert to report any suspicious activity.

According to the Tom Fulcoloro of the Seattle Bike Blog, the tacks were found on the eastern high-rise of the I-90 bridge where it enters Mercer Island.

“People suspect it has happened before,” said. Fulcoloro. “When multiple people are having flats, six or seven, clearly something is going on.”

Another blogger, Gary Powell, whose blog is “Bike to Work,” said he bought a magnet stick Oct. 15 to clean up some of the tacks.

He picked up a lot of “junk,” but it wasn’t until he reached the east side of the bridge that he ran into some people who had found about 20 tacks, which he then added to his magnet stick.

Powell said he did not get a flat, but his friend Tim has hit tacks for the last month.

Then, on Oct. 14, about a dozen people ended up with flat tires.

“There were people all over with flats,” Powell said.

He said the next day he walked the entire trail across I-90 doing a slow sweep with the magnet.

Powell said he lives in Bellevue and commutes to South Lake Union each day by bike.

Jason Kintner, parks superintendent for the city, said he has had between six and a dozen emails about the tacks. He notified both the police and the Washington State Department of Transportation.

“The Seattle Bike Blog really helped us in this incident,” he said. “The Cascade Bicycle Club has also put out the word to its members.”

Fulcoloro notes that simply having a flat tire on a bike is not always a minor event.

“When you hit a tack that big, it is dangerous,” he said. “Those tacks are big enough to have a full-on blow out. People might think they are just annoying people. It is pretty angering to think people might get hurt.”

Kintner notes that it is a long stretch between the eastern and western entrances to the Mercer Island path. It is hard to watch it all.

But as the leaves fall, more parks people will be out removing the leaves from the path.

They will be on the lookout, he said.

During the 2011 Seattle to Portland ride, someone scattered tacks on the roadway across a four-mile stretch on Highway 30.

The Oregonian and other news sources have covered similar incidents across the country.

If you have any information, contact Kintner at Jason.Kintner@mercergov.org or call the Mercer Island police non-emergency line at (425) 577-5656.