A fault with an electrical cable is being blamed for an underground explosion that blew manhole covers off a street in the city's Chinatown neighbourhood on Sunday.

Three manholes blew off King Street between Alexander and Logan avenues around 2:30 p.m. Sunday.

Manitoba Hydro spokesman Jim Peters said the investigation is still in the preliminary stages, but officials believe there was an electrical fault in an underground cable called a secondary line.

"In most overhead and underground distribution lines, there's a primary line, which is simply a higher voltage line, and a secondary line which is a lower voltage line," he explained Monday morning.

"So there was a fault in the secondary cable underground. But we haven't been able to determine why that would have, in any way, created the scenario yesterday."

Streets were closed for several hours as police, fire, paramedic and Manitoba Hydro crews tried to figure out what happened.

"I heard it explode, and then the building was shaking and then I run out and see on the ground, smoke coming out [of the manhole] and also the cover — it moved to the side," said Sylvia Woo, who was working at the Wah Hing Grocery on King Street.

"Everybody heard it," she added. "We run out to see what happened. At first we think about maybe it's a car accident, until we see the smoke…. The smoke coming out is a little bit yellow, a little bit yellow and white."

Police and firefighters showed up moments later and told people in residential and commercial buildings in the area to leave, Woo said.

No one was hurt. The only damage was to the surface of a sidewalk on King Street.