The city says the water main break at Yonge and Wellington Sts. may take up to eight hours to fix.

The northbound lane of Yonge St. reopened ahead of the morning commute, but the southbound lane between King St. and Wellington St. is still closed.

The break happened around 3:30 a.m. Thursday morning, according to Toronto police, and crews have been on the scene since 4:45 a.m. Police said water was bubbling up onto the street, turning the stairs to the subway at Melinda St. into a waterfall.

The Melinda St. exit and the Commerce Court entrance have been closed by the TTC until further notice. TTC cannot confirm if the exits will reopen by Friday morning’s commute.

Director of distribution and collection for Toronto Water, Bill Shea, says it has been a lengthy proccess fixing the break for a few reasons. First, crews had to isolate which water main it was, then find the corresponding valves to stop the water flow (Shea said they inspected at least 12 different valves) and utility locators had to be on scene to pinpoint hydro and gas lines.

After locating the water main, crews had to find out just where the leak was coming from.

The answer: a pipe dating back to 1887.

However, Shea said the fact that the pipe is old isn’t enough reason for a water break. He thought most likely that it was caused by a shift in the ground.

Yonge St. was originally closed both ways between Wellington St. W. and Melinda St.

Police from 51 and 52 divisions cordoned off the area while Toronto Water crews work on a fix. The 97 Yonge St. bus continues to divert southbound via Adelaide, Church and Wellington Sts.