The London Fire Brigade was alerted to the blaze inside a fourth floor property in London Road at 11.40am on July 10.
Firefighters were informed that two pets, a tortoise and a dog, were inside the flat.
The animals were found hiding under the stairs from the fire, which was burning in one room.
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They were returned safely to their owner.
The fire has since been confirmed to have been started accidentally by the tortoise after he knocked over the heat lamp, causing it to fall onto hay in his pen.
Crews from Mitcham, Wimbledon, Tooting and Wallington fire stations were stood down at 12.22pm.
