No subway service was running between Islington and Ossington stations on the west end of Line 2 early Tuesday, the TTC said.
A transit agency spokeswoman said work to install new rail in the area of High Park station had been delayed overnight, forcing closures along a long stretch of track.
According to the TTC, shuttle buses are running from Kipling to Ossington.
The spokesperson could not say when regular metro services would resume.
