Toronto transit is having a week.

Just one day after a train derailment caused a six-hour subway delay during the morning rush hour, UP Express service was suspended for more than five hours due to a signal problem.  

We are working on the signal issue, however #UPExpress service is expected to be suspended for the next 2-3 hours. Shuttle buses are still running between Union (Station St., near Goodlife Fitness) and Pearson (terminal 1, near columns Q2 and Q4). pic.twitter.com/ZShTS1GkzV

— UP Express (@UPexpress) February 14, 2020

The UP Express Twitter account first reported the issue at 4:42 a.m. this morning.

"#UPExpress train service is currently suspended due to an ongoing signal problem," they wrote. "Guest travelling to and from Pearson Airport and Union Station will have access to a GO shuttle bus. Weston and Bloor guest should make their way to the nearest TTC subway."

They continued to tweet that service remained suspended for most of the morning, until they reported that the issue had been resolved at 11:05 a.m. and service resumed at 11:30 a.m.

The signal problem has been resolved. Regular #UPExpress service will begin from Union at 11:30, and from Pearson at 11:42.

— UP Express (@UPexpress) February 14, 2020

Some Toronto residents suspected the issue was due to this morning's brutally cold temperatures, but Metrolinx spokesperson Nitish Bissonauth told Global News the problem was likely a mechanical issue and had nothing to do with the weather. 

And while the occasional transit issue is certainly bound to happen, Toronto commuters are particularly frustrated with how chaotic this week has been. 

"UP Express is down too?!" one resident tweeted this morning.

"Toronto transit is a disaster."

Meanwhile, Toronto Mayor John Tory has called for an investigation into how the city’s transit agency handled the derailment that stopped service between St. Clair West and Union stations yesterday. 

At a news conference Thursday morning, Tory said there was an evident lack of communication and that the TTC should look into refunding customers who paid their fare but didn't receive service, according to Global News. 

Yesterday's transit meltdown came less than one month after another derailment caused a massive TTC shutdown.