A group of around seven people mysteriously emerged from the sewer system in Gravesend, police say.

The mystery unfolded just after 2 a.m. Friday near McDonald Avenue and Collin Place.

Surveillance video from the Flatbush Scoop shows the group exiting the manhole one by one before gathering near two parked cars, where they appear to remove their soiled clothing and clean themselves off.

Officers were captured on Citizen app video working to unravel the mystery around 10 hours later.

The NYPD says it is unclear how long the group was in the sewer system or what they were doing there. No arrests have been made as of Friday evening.

Friday morning's mystery follows a man's overnight disappearance into the sewer system in Dyker Heights around six months ago.