Updated

Crews were waiting for an area to cool off under the streets of downtown Savannah before they could start determining what caused an electrical explosion Monday that blew off manhole covers and knocked out power for hours to many stores, restaurants and homes.

By late Monday, almost all streets had reopened, as did stores and restaurants evacuated after the blast, said police spokesman Gene Harley. Also, crews had restored power to about 95 percent of the homes and businesses that had gone dark, said a Georgia Power spokeswoman. No injuries were reported and there was only minimal property damage, officials said.

Police evacuated the historic downtown district after getting calls about the explosion around 8:49 a.m., Harley said.

"I didn't see it happen, but I heard an explosion and then black smoke started billowing out of the ground from the manhole covers," said city spokesman Bret Bell, who was about a block away at City Hall.

The fire department sprayed foam to cool down the affected areas, but the blast site was still too hot late Monday for crews to access the underground electrical cable network to determine the cause, said Georgia Power spokeswoman Swann Seiler.

In August, an underground electrical fire just blocks away also spewed smoke through manhole covers and cut off power downtown. That problem, Seiler said, was caused by a fault in the underground network system.

Georgia Power is in the second year of a $50 million five-year upgrade in the underground power network downtown, Seiler said.

"I think this will probably trigger some sort of larger public discussion," Bell said. "I think the public will want to know exactly what Georgia Power is doing."

The affected area included River Street, the site of many of Savannah's tourist attractions, shops and restaurants.

"We are very fortunate that, in this high traffic area, with three manhole covers coming up, there were no injuries and relatively no property damage," Seiler said.