A crack in the rail welding on Wednesday morning caused Ottawa's Confederation Line trains to move slowly near Hurdman station for much of the day.
While OC Transpo's twitter account announced the possibility of "slight delays" due to track maintenance, it did not say what the issue was.
However, city officials confirmed to CBC late in the day that "a break occurred on a weld" and that the repair would take place on Wednesday evening.
"The rail line was inspected by a rail specialist and trains can travel safely along the line at a reduced speed," according to an email attributed to Michael Morgan, the city's director of rail.
Last week, OC Transpo director of operations Troy Charter told the transit commission that there were four main issues with the $2.1-billion Confederation Line, including two computer issues, the doors, and the switches.
Whether the cold weather was a factor in causing the welding to crack is unclear.