AURORA, Colo. -- Environmental experts are investigating a mystery ailment at Aurora Police Headquarters after several employees complained about respiratory problems.

Some of the employees blame their health issues on mold contamination.

However, the city of Aurora said it has not found a mold problem.

"We've had several employees that have come forward to express concerns about coughing and asthmatic symptoms, those types of things," said Kin Shuman, director of human resources.

"Some officers are concerned about it being a sick building," said Don James, president of the Aurora Police Association.

James works in the building. When asked about his health, he said, "I have not noticed any problems but have heard of others who have."

"I would like very much to help them. I know they believe strongly that there is a mold issue in the building," said environment specialist Don Roche. "(But) the data is just not there to support that."

Environmental experts said they did find slightly elevated levels of mold above the ceiling tile in the supervisor's office and in a crawl space near the property division in the basement.

"They, again, do not rise to the level of a mold problem," Roche said.

Still, the city plans to remediate those areas as soon as possible.

An estimated 200 people work inside the police headquarters building, some in cramped quarters. That has led some to wonder if excess carbon dioxide is an issue.

The city has checked for elevated levels of carbon dioxide, and has tested for chemicals and asbestos. All tests have come back negative, so the city has asked for its employees' help.

"We're trying to go into the workplace and have them tell us where they work, and where they think some of the issues are in the building," Shuman said.

The city of Aurora has spent more than $2,400 on tests to try to find the problem.

Two years ago mold was found growing under a carpet in the professional standards area on the second floor. That mold was traced to a leak in a pipe under a sink on the third floor.

Last year, mold was found in a supply closet in the fraud unit. That mold was traced to a leak in the flashing around a vent pipe on the roof.

In both instances the leaks were fixed and the mold was removed.

City officials hope that by working with employees, they'll be able to get to the bottom if this latest issue whether it's mold related or not.