Flooding in Union Station Wednesday night, which turned the subway platform into an impromptu waterfall, appears to be unrelated to the heavy rain that swept Toronto.

A water main broke at Bay Street and Front Street West at about 10:30 p.m., sending the flood waters into the subway station.

The water rushed down the staircases into the mezzanine, then turned the inside stairwells and escalators into rapids.

Rafi Tchalikian said that when his subway train arrived at Union station, "there was a sound of, like, water rapids, and it was just wild. So I look up, and water was just flying down the staircases, flying down around the escalator and there was subway workers, like, looking around. The elevator was open and it looked like a waterfall," he said.

"There was [police] officers, like, kind of shaking their heads and TTC workers trying to figure out how they're going to get everybody out of the station, off the property," said Rafi.

The TTC closed the station for the rest of the night to clean up. Trains continued to run on the Yonge-University-Spadina line but didn't stop at Union.

"Our crews were down there all night mopping and squeegeeing and making sure the station would be ready for this morning's commute," said TTC spokesman Brad Ross.

Elsewhere in Toronto the Bayview extension was flooded by the heavy rain.

The Toronto and Region Conservation Authority is warning that rain and melting snow have resulted in swollen rivers and streams that should be considered dangerous.

The rain is expected to end Thursday afternoon and temperatures will drop.