Metro bosses had to pull off a carriage today after someone defecated on the train.
Tyne and Wear Metro said some of the delays to today's service was due to what had happened.
In a Tweet to a customer, they said: "Sorry, the train has been travelling up from Sunderland with only the rear car in operation as someone has defecated on the train and has covered three seats with faeces.
"The train has to go into the depot to be cleaned up. Sorry for the inconvenience."
Earlier in the day the service said: "There are delays of up to 30 minutes between the Airport and South Hylton and up to 20 minutes between St James and South Shields, this is due to lack of available trains."