TALLAHASSEE, Fla. - Boom - with an explosion heard several miles away and felt for several city blocks, an Air Force explosives team detonated a Second World War-era bomb unearthed at a construction site Wednesday near the Florida State University campus.

The blast went off about 9:30 p.m. in a trendy neighbourhood with restaurants, shops and a brewery less than a mile from the state capitol. A construction crew unearthed it hours earlier and called Tallahassee police.

"It was like really loud thunder, and you could hear the windows shake," said Shannon Glassner, a Florida State sophomore who lives in a sorority house about three blocks from the site. "A couple of people screamed. I could hear them come out of their rooms and run into the hallways."

Earlier, the Tallahassee police bomb squad supervisor, using binoculars from a distance, examined the artifact and determined it could indeed be a bomb, police spokesman David Northway said.

"They didn't get very close to it," Northway added.

Several streets around the construction site were cordoned off with yellow tape, and officers blocked traffic and pedestrians from approaching. An ambulance and a firetruck were on standby.

In a multistory apartment just beyond the yellow caution tape, women on several floors hung out of their windows asking officers questions, including how big the potential bomb is. An officer stretched both arms wide.

"Will we be notified if there's a concern?" a student yelled from a second-story window. An officer replied, "The entire building will be evacuated."

Kaylee Madden, a junior sociology major, lives directly across the street from one evacuated apartment complex.

"It's sketchy," she said, with a laugh. "I heard it might not work. It's old. I'm not that scared unless it's actually going to blow up. It's weird."

But later the 325th Explosive Ordinance Disposal Flight out of Tyndall Air Force Base in Panama City arrived and confirmed it was a Second World War-era bomb. Police haven't indicated how it came to be there. The Museum of Florida History website says Tallahassee had an airfield during WWII that was used for training.

The neighbourhood was cleared, a large hole was dug and the bomb covered in dirt to ensure fragments wouldn't be sent flying. The blast shook buildings within a few blocks of the site.

Glassner said that Florida State sent an email to students just moments before the bomb was detonated.

"I had just read it, and about 15 seconds later it went off," she said, adding she wasn't particularly frightened by the blast. "I'm more just amused, and I'm worried about if there's going to be any more and how that was overlooked before."