They said it sounded like a bomb went off in downtown Atlanta.

A loud boom. Fire. Smoke. Manhole covers flying off on Peachtree Street.

“There was fire,” witness Desiree Bennett told Channel 2 Action News. “We could not believe what we saw.”

Georgia Power says what Bennett saw was the end result of an underground explosion that blew the manhole covers off the street and sent smoke coming up from underground.

People heard the explosion around 7 p.m. Monday several blocks away.

The blasts shut down Peachtree Street between Mitchell and Alabama, and Martin Luther King Jr. Boulevard between Pryor and Spring streets.

“We had a fire in some electrical cables located in a network underground vault,” Carol Boatwright with Georgia Power told News/Talk WSB. “The fire resulted in five manhole covers being blow off.”

Bennett saw two of them. Once the second one popped, she had enough.

"It broke in two (in) mid-air. So that was enough to tell me to leave," Bennett said.

The explosion may be related to some underground repairs. Electricity was shut off to about 10 downtown buildings.

Police reopened most of the roads by late Monday night. But Georgia Power crews were still working on Broad Street.

Boatwright says no one was injured from the blast.

"The people that I talked to believe that everything is safe at this point," said Boatwright.

It could take a couple of days for crews to figure out exactly what caused the fire.