The Northern line has been suspended while a dog is rescued from the tracks.
Services were disrupted at about 10.45am with one passenger saying an announcement of a 'trespasser' on the tracks had been broadcast.
It has since been confirmed on Twitter that a dog is being rescued.
Services are suspended from Morden to Kennington.
There is no estimate on when the situation will be resolved and passengers are advised to use alternatives routes.
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