The O-Train is back in service after part of a train left the tracks at the Carleton University station Monday afternoon.

Twitter user Henry Guardado tweeted just after 3:15 p.m. Monday: "O train derailed? #nOtrain yet again..." with a photo of the northbound O-Train appearing to veer slightly off-course.

On Monday, passenger Kate Mckeage tweeted it felt like "a big bump and some shaking" and that one person was being checked out by paramedics.

"The train was going very slow, otherwise it could have been worse," she said.

The train was running again as of 8:45 a.m. Tuesday after a night of inspections, OC Transpo said.

Mckeage said the end of the first O-Train car and beginning of the second was around where the train went off the tracks, near the split in the track at Carleton.

She told CBC News she overheard OC Transpo staff discussing signalling issues with the train, which she said had been a few minutes late getting to her station and was going slower than normal.

OC Transpo said Tuesday the cause of the incident is still under investigation.