"Members of the public heard a loud noise and we want to reassure the public there is no cause for alarm," police said.
Railway and public transport services were briefly suspended.
Buses were unaffected. Cordons have now been lifted.
Jess Kirk wrote on Facebook: "My husband was on the train it got locked down there. The train conductor said it's a bomb scare and the bomb squad is coming in, so the station has been evacuated."
Another Facebook user, Claire, posted: "They just blew something up I was sent back and I need to work at the community Centre so I am sitting waiting around the corner. Big bang."