DULUTH, Minn. — About a dozen jets from the Air National Guard 148th Fighter Wing have been grounded because of damage apparently caused by debris on the runway at Duluth International Airport.

Fighter Wing Capt. Jodi Kiminski says crews regularly check for foreign object damage and recently found metal fragments have caused problems for the F-16s.

Kiminski tells WDIO-TV (http://bit.ly/1zCY5mA) the fragments are believed to have been shed from the bristles of a snow removing machine used on the airport runway. Kiminski says the jets have been grounded for about a week and are being repaired.

Spokeswoman Natalie Peterson of the Duluth Airport Authority says the bristles were invisible when released on the tarmac. Peterson says only fighter jets were affected, not commercial aircraft. She says the machine was immediately pulled from service.