A fatality near the Whitby GO station had trains stopping at Ajax station on the Lakeshore East Line for about four hours Sunday afternoon.
Metrolinx spokesperson Anne Marie Aikins says the incident happened around 12 p.m., but no further details have been released.
Trains were running from Union Station to Ajax GO station, then those who wanted to head further East were able to take a shuttle bus.
Regular service resumed just after 4 p.m. Saturday.