Part of Stoney Street was sealed off on Tuesday evening after a hole appeared in the road surface.
Southwark Police say that they did not receive any reports from the public about the incident but officers on patrol may have taped off the affected area.
"It appears that this is a sewer collapse," says Cllr Barrie Hargrove, Southwark's cabinet member for transport, environment and recycling.
"The hole is about 3 by 4 metres and about 1.5 metres deep.
"We are contacting Thames Water to get them there as soon as possible.
"In the meantime we have plant on site and will excavate to expose the sewer and remove all loose debris.
"It's difficult to estimate exact timescales for repair but we imagine it will be a number of days to rebuild the sewer.
"Obviously we can't backfill the depression in the meantime."