Authorities are trying to figure what caused a huge boom that shook buildings and windows in the state of Alabama in the past week. Local residents flooded 911 lines after the “Bama Boom” shook houses and rattled windows, and no one seems to have a satisfactory explanation for what happened.

And Alabama wasn’t the only place it was reported. Booms also happened in Idaho, Colorado, Michigan, and New Jersey, as well as in Australia and the Middle East. There have been 64 reports of booms so far in 2017, and authorities offered no positive explanation when asked.

“Loud boom heard: we do not see anything indicating large fire/smoke on radar or satellite; nothing on USGS indicating an earthquake,” said the Birmingham National Weather Service in a tweet.

“Has anyone heard a loud explosion in west Blount County? We’ve received several calls between Spunky Hollow Rd and Cannons Crossing. Law Enforcement is currently patrolling the area,” Blount County in Alabama posted on its Twitter account.

“We do not see anything indicating large fire/smoke on radar or satellite; nothing on USGS indicating an earthquake,” the USGS posted on Twitter. “We don’t have an answer, and can only hypothesize with you. 1) sonic boom from aircraft; 2) meteorite w/ current Leonid shower?”

The boom in Colorado, like the Bama Boom, shook homes at around 9 p.m. on Nov. 20. The local police chief even contacted the Air Force and Federal Aviation Administration to figure out what was going on, but they said they weren’t the cause, and the fire department couldn’t figure anything out either.

“It was just like boom and the trailer shook, and I thought, ‘what the heck was that?’” said Ray Armijo, a resident who has served in the military, according to a Tech Times report. “It kind of scared me a bit.”

The most popular theories being proposed include a supersonic jet breaking the sound barrier, or a meteor exploding in the atmosphere. Authorities say it’s not being caused by earthquakes or the weather.