OAK GROVE, Minn. — Authorities in the north metro are investigating after a golf ball struck a mosquito treatment helicopter last week.

The chopper, flown by a contractor with the Metropolitan Mosquito Control District, landed safely in East Bethel just before 10 a.m. Friday, according to the Anoka County Sheriff’s Office.

The pilot said they saw a golf ball “fly at the helicopter” and, upon landing, found it had been damaged, according to the sheriff’s office. The pilot was uninjured. 

The helicopter was over the Refuge Golf Course in Oak Grove when the ball struck it. Deputies and course employees unsuccessfully attempted to identify the person who hit the ball.

“The safety of our employees and our contractors is my top priority,” Metropolitan Mosquito Control District Executive Director Daniel Huff said. “I appreciate the work of the Anoka County Sheriff’s Office for taking the lead in this investigation.”

Huff added that “helicopters are an essential part of mosquito control operations” and that larval control by helicopter is “the safest and most effective way to protect the public from disease and annoyance caused by mosquitoes.”

The Metropolitan Mosquito Control District keeps an updated list of planned helicopter treatments on its website.

The latest report from the Metropolitan Mosquito Control District, issued in early July, said mosquito numbers are well below the 10-year average, despite the wet spring Minnesota experienced. The district said early June saw the largest numbers so far this year.

Earlier this month, mosquitoes in Anoka and Ramsey counties tested positive for West Nile virus, a flu-like illness that can also cause more serious symptoms.