An enormous explosion lighted up the sky and set off a fire at a naval munitions base in Charles County, causing damage but no injuries, authorities said.

The incident occurred about 10:25 p.m. in one of 1,600 buildings at the Indian Head Division of the Naval Surface Warfare Center -- many of which are used for the storage of explosive materials, said Chris Adams, a spokeswoman for the base.

Details were sketchy about the size of the explosion and how it was caused, she said.

"It appears to be limited to one storage facility. . . . We have a fire station on the base that responded. The local fire department asked if we needed assistance and we were able to say no," Ms. Adams said.

The fire was extinguished by the base firefighters, she said.

Witnesses -- some as far as 7 miles away -- reported seeing the sky turn bright yellow or orange when the explosion occurred, followed by three or four loud booms. Some said the light from the explosion made the sky resembled the sunrise or bright fireworks.

"I was on the phone and all of a sudden the sky turned bright yellow," said 15-year-old Melissa Hepner, who lives on Mason Springs Road near the base. "It really scared me. I'd never seen anything like that before. It sounded like something was hitting the house."

The base is a testing ground for explosives and also disposes of old munitions.