NORTH HOLLYWOOD (CBSLA.com) — Police on Wednesday were unable to determine the source of a reported loud explosion in the North Hollywood area of the San Fernando Valley.

Calls about the reported blast came in around 9:30 p.m. on Tuesday, according to Sgt. Glenn McNeill of the Los Angeles Police Department’s North Hollywood Division.

“We sent units out, we looked, but we could not find the cause of the explosion, gunshot, whatever it was,” McNeill told KNX 1070 NEWSRADIO.

Residents on Twitter reported hearing a loud bang throughout the area surrounding North Hollywood and Studio City.

The BIG #boom in #NorthHollywood vibrated my couch. Police are perplexed. I say check the meth lab down the street.

—
LaFern Cusack (@laferncusack) January 09, 2013

@LAist Any idea? RT @filmester Totally heard huge explosion somewhere in #NorthHollywood right now, and now lots of sirens and helicopters.

—
Josh Weinberger (@kitson) January 09, 2013

Seriously, any leads on what the hell this boom was in North Hollywood? Im a shook up a bit

—
Raj Rawal (@RajRawal37) January 09, 2013

While speculation about the source of the noise ranged from an explosion at the North Hollywood Metro station to an extraterrestrial invasion, McNeill said whatever it was, it caused quite a commotion.

“Definitely something happened, something very loud,” he said. “You know when you get that many calls, there’s definitely something going on.”

Twitter users also reported hearing at least two sonic booms in Utah around the same time Tuesday night, but it remained unclear if those booms were related to the sound reported in North Hollywood.

A similar sound was reported in January of 2011 after Mylar balloons became entangled in power lines in the 6200 block of Riverton Avenue. The balloons caused a flash and a loud boom heard across a wide stretch of North Hollywood.