SPT, which runs subway services in the city, announced on social media that services on the line had been stopped due to a broken down train at Cowcaddens.
While the Outer Circle is not running, services on the Inner Circle are running as normal.
A post on the SPT Twitter page said: “Maintenance team is working to get it moving. Services on Inner Circle running as normal. Apologies for the inconvenience. Will update when Outer Circle resumes.”
