British Transport Police said a "small number" of people had been treated at the scene.
A police spokesman said: 'Southgate Tube station is now closed whilst officers respond to a suspicious package.
A police statement confirmed that officers remain at the Southgate station and enquiries are "ongoing" to established the cause of the reported minor explosion. "We are not aware of any serious injury", wrote the Metropolitan Police Department.
People are being asked to avoid the area.
The force tweeted: "Southgate Tube station is now closed whilst officers respond to a suspicious package".
Haluk Ozkan was about to get on a bus outside the station when he smelt something burning.
City worker Darren Yarlett, 36, told the Evening Standard that he was attempting to drive home in the area, but found the roads had been tapered off.
British Transport Police added that "we do not believe this to be terror related".
At least five people have been injured after an explosion at an underground train station in north London.
Police say no cause has yet been established. "The Met Police and BTP are working together to establish the full facts".