A large hatch of mayflies caused a head-on collision on U.S. 61 on Sunday, July 15.

The accident occurred about 11:30 p.m. on the Hasting Bridge.

A slippery layer of dead bugs over the runway caused a driver to lose control of the vehicle and collide into an oncoming vehicle.

The film of dead mayflies was 2 to 3 inches thick, according to Kent Barnard, spokesman for the Minnesota Department of Transportation.

Mayflies are usually seen near water during the summer months. They are attracted to light, making them prone to getting run over by drivers at night.

Transportation officials closed the bridge for about an hour to remove the bugs with a plow and pour sand over the area.

The people involved in the accident suffered minor injuries and were transported to the closest hospital for evaluation.

Although it is common to see large amounts of mayflies near lakes and rivers during summer, accidents of this kind are rare, Barnard said.

Danya P. Hernandez can be reached at 651-228-5116. Follow her at twitter.com/DanyaPH.