Fire officers investigated reports of a fire after someone phoning remotely by Skype reported smoke in an upstairs bedroom.
Wimbledon firefighters were called to a second floor flat in Trewince Road, Raynes Park at 6.30am this morning.
But when they arrived at the property, a mixed-use nursery and flat, they discovered it was a false alarm.
A fire officer from Wimbledon station said: "We did a very strange one this morning.
"From a Skype screen someone had seen smoke but the one person who was in the nursery was fast asleep."