Lightning sparked five wildfires over the past month in the Sabine and Cameron Prairie national wildlife refuges in southwest Louisiana, the U.S. Fish and Wildlife Service announced Thursday.

The first fire started June 18, and the most-recent fires began Tuesday, according to the Fish and Wildlife Service.

More than 6,000 acres have been affected, but no facilities or structures are at risk, according to the Fish and Wildlife Service. The service reported that fire crews continue to monitor the fires and drop water from helicopters as needed.

Marsh fires sparked by thunderstorms are common in the summer, according to the Fish and Wildlife Service.