IMPERIAL, Pa. - Brazen hunters have illegally sneaked onto land surrounding Pittsburgh International Airport in search of deer, presenting a serious threat to aviation safety, officials said.

"All it takes is one incident," said Gary Fujak, a Pennsylvania Game Commission wildlife conservation officer based in Allegheny County. "If a slug hit a 737 on the airfield, that wouldn't be a good thing, but that could easily happen with one small mistake."

The problem is that the 9,000 fenced-in acres are teeming with hundreds, if not thousands, of deer, and that is proving to be too much of a temptation for some hunters.

"There are certainly some very nice bucks in there - bucks of a lifetime - and many have never been hunted before," said Craig Swope, a district supervisor and wildlife biologist for the U.S. Department of Agriculture.

"It's not uncommon to see 40 or 50 together in a two-acre field," he said. "That's not normal and, for some, hunting is worth the risk of being caught."

On Tuesday, county police cited a 64-year-old Sewickley man and his 41-year-old son after police said the son was inside a gated area of the airport, dressed in camouflage and armed with a rifle.

Officials also worry that the deer pose a risk to aircraft.

During the last 20 years, planes have hit deer several times, according to Brad Penrod, airport authority executive director.

Penrod has seen propellers damaged on a turboprop plane and a deer carcass thrown into a small plane's cockpit, he said.

Swope, who plans to submit a wildlife management plan to the Allegheny County Airport Authority next week, said the deer population "is through the roof."

Pittsburgh International handles its own deer control, unlike other airports in Pennsylvania, which contract with the federal agriculture department.

The airport authority uses about a dozen employees who are experienced hunters to kill deer or drive them from the airfield as needed, Penrod said. The carcasses are given to a meat processor, who gives the meat to local food banks.