Dramatic pictures from the scene in Durham Place, Chelsea, show the mid-terrace buildings reduced to rubble after the “extremely loud” crash on Monday evening.
Firefighters said two four-storey properties that were under construction collapsed to the ground.
Three properties on the street, including one next door to the collapsed buildings, are currently undergoing basement excavations
A spokesman for Kapital Basements, a company which is carrying out the basement dig, said the firm’s work had nothing to do with the collapse.
Large-scale basement developments, often including the construction of entire new floors under the footprint of an existing house and garden, have become relatively common in London’s wealthy neighbourhoods.
Some of the more lavish constructions include multiple basement levels and can go as deep as 18 metres underground