No one was injured after an explosion and intense fire in east Ottawa Monday night.

Fire officials say the hydro vault at a hydro sub-station on the National Research Council's campus on Montreal Rd. exloded just before 9:00 pm.

Rehanna Goveas lives across the street. She thought it was her kids playing.

"I heard a loud noise and the (kids) said 'oh it's my iPad on too loud,'" she says. After smelling smoke, she investigated further.

"I looked through my laundry room window and there was a big fire."

Rolland Huard lives in an apartment building close to the campus.

"I saw a huge flash, thought it was lightning," he says.

"It lit up the whole area, and about a second later, I heard a large boom sound."

Fire crews were on scene quickly, but couldn't fight the expanding fire until hydro crews shut the power off to the sub-station.

"Once we got the water on it, it didn't take long to put it out," says District Chief John Davis.

"There was a lot of smoke and the flames were licking 75 feet in the air, so it looked spectacular."

Goveas and her family watched the fire grow before finally deciding to leave.

"We were a little afraid of it and we decided to go because we don't feel safe...we're right across the street," says Rehanna's daughter Danika.

Davis says the oil in the sub-station fueled the flames. Hazmat crews were on scene monitoring the air quality but there were no health concerns about the smoke that spread into neighbourhoods nearby.

The official cause of the fire hasn't been released, but neighbours reported seeing sparks on hydro lines prior to the fire starting. There's also no word on damages.

Hydro One crews assessed the damage on Tuesday. The NRC says repairs are expected to take several days. Back up generators are powering the 50-plus buildings on campus. They're hoping to have main power restored by the end of the week.