If you heard a loud boom this afternoon, you weren’t alone.

Many people across the Bay area reported hearing the loud noise.

Residents in Hillsborough, Pasco and Polk counties also reported feeling the ground shaking.

Was it an explosion? A military operation?

Spectrum Bay News 9 reached out to law enforcement agencies to find out the cause.

Many agencies said they didn’t know.

A Pasco County Sheriff’s Officer spokesperson said the agency received dozens of calls about the boom. Some callers reported seeing military-style jets around the time of the boom, but Pasco deputies were not able to confirm that.

It seems, for now, the loud boom remains a mystery.