Something shook up Flagler County in northeast Florida on Friday morning, provoking dozens of reports of homes shaking and a sonic-boom-like noise.

Officials had no idea what rattled the region and may never figure out what happened, said Flagler County emergency management chief Troy Harper.

The most likely explanation is military activity offshore, Harper said.

The Navy drops live bombs on a range in the Ocala National Forest and over Lake George, both of which are west of Flagler County, he said.

Don't blame it on the Navy, said Navy spokeswoman Miriam Gallet. "We have nothing going on," she added.

Some residents said the trembling caused their garage doors to rattle, and others said their homes shook, Harper said.

The National Earthquake Information Center in Colorado said it also received calls about the incident, but monitoring equipment showed no seismic activity in Florida.

There were no reports of injuries or damage, Harper said.

The booming started about 9:40 a.m. and initially was concentrated in an area about 8 to 10 miles long and about 2 miles wide, about 75 to 80 miles north of Orlando.

But as news reports of the event spread, more and more people called to say they had experienced the tremor, Harper said.