BUFFALO, NY – National Grid Corp. hopes to learn within a few days what sparked a fire involving some underground electrical cables, which resulted in an explosion that sent a manhole cover soaring several stories in the air in downtown Buffalo on Sunday.

WGRZ-TV Photojournalist Dave Harrington captured the loud explosion and rocketing manhole cover on video.

"They pulled all the bad cable out and it will be sent off to a lab for testing and examination," said National Grid Spokesperson Steve Brady."However, sometimes it is burned up so badly that they are not able to completely tell. But it's going to take at least a couple of days to determine before we have an answer."

Common causes generally include aged cables, excessive salt and water from a harsh winter, which can get in and deteriorate them, or even rats chewing on them, according to National Grid.

According to Brady, it is common for there to be a rapid buildup of heat and gas during a fire in an underground conduit, which is after all a confined space.

On somewhat rare occasions, there can be an explosion with enough force to move a heavy manhole cover.

Extremely rare, he says, is when a cover is sent rocketing into the air.

."In most cases what will happen when a cover comes off is it will essentially pop but maybe move a couple of inches or a couple of feet….the one we witnessed (Sunday) is, fortunately, exceedingly rare."

In recent years a number of utilities have gone to slotted manhole covers to allow the gas to be released less violently, including National Grid.

"We actually have very few solid manhole covers left in our system," said Brady, who said he was uncertain as to the type of manhole cover involved in Sunday's incident.

At the same time, however, a potential downside to slotted covers is the potential decrease in their ability to keep out that, which commonly leads to fires in the first place.

"Especially the debris and road runoff that goes down into the those vaults," Brady said.

National Grid says there it still has more work to do at the intersection of the Pearl and Tupper Streets where the explosion occurred.

"The underground structure under will have to be rebuilt due to the damage it sustained," said Brady. "Right now there's a very large steel road plate over it and there's cones on top of that, so cars can get around it but we don't want them driving right over it."