A Department of Defense official confirmed Thursday that fighter jets flying out of Maryland caused the tremors felt on Long Island and elsewhere on the East Coast.

Officials say two jets were conducting a developmental test in the Atlantic Test Range off the East Coast. They reportedly reached supersonic speeds and created a sonic boom.

Residents in both Nassau and Suffolk reported hearing the loud noises and feeling tremors early Thursday afternoon.

Many people initially said they thought they'd felt an earthquake, but the federal government announced later in the afternoon that two fighter jets -- an F-35C and an F/A-18 -- likely created the boom after launching from a naval air station in Maryland.

Scientists told News 12 Long Island that while it's not uncommon to feel a sonic boom this time of year, it is uncommon for people to feel it over such a wide area.