Winnipeg city crews are working to fix a water main break that flooded a section of the city's most famous intersection, Portage and Main, on Thursday morning.

The water main break, which happened around 9 a.m., turned part of the intersection and a stretch of southbound Main Street into a muddy lake.

Some street lanes were closed for hours as water came up to the curb, flowing over the curb in some places.

"I came out earlier in the day too and it was bubbling up all over the street. There was like a little river running down Main Street," said William Dumont, who works near Portage and Main.

The southbound lanes reopened at Portage and Main by noon, but the curb lane remains blocked, the City of Winnipeg says. 

While the water has come down, brown residue remains on the street. Motorists are being advised to avoid the intersection until it's cleaned up.

The leak happened in a large cast-iron main that was installed in 1908, says Tim Shanks, manager of water services with the City of Winnipeg's water and waste department.

"It was a break on a section that doesn't have any customer connections, so we were able to isolate the water main break without putting anyone out of water," Shanks told reporters.

While crews have the leak under control, no timeline was given for when it will be fully repaired. As well, the cause of the break has not yet been determined, Shanks said.

"The specifics of the actual break — whether it was a crack around or a pinhole, that sort of thing — that won't be determined until we actually complete the repair," he said.

People may find discoloured water in nearby buildings as water flows return to normal, say city officials.

"We received notice not to drink any tap water until everything was given the all clear," said Dumont.

Eshel Tree Portage and Main flood

Buckets collect water dripping from the ceiling outside Lee Kyungho's convenience store, Eshel Tree, in the underground concourse below Portage and Main. (Samuel Rancourt/Radio-Canada)

Some of the water has seeped into the underground concourse at Portage and Main, including the Winnipeg Square shopping centre.

The city says at least one business inside Winnipeg Square may have experienced water damage, but no damage estimate is available at this time. 

Kyungho Lee, who owns a convenience store there, said he called the city after someone noticed water dripping from the ceiling of his shop around 9:30 a.m.

"One customer who passed through this way, he said to me, 'The water is coming out,'" Lee said. "I checked the display shelf and the water is coming out from the ceiling."

Aside from having to move some products away from areas where water was dripping, the flood has not affected the business too much, he said.