Mole people? Mario brothers? Ninja turtles? Bizarre sightings of people entering ad leaving the city’s vast sewer system has left residents wondering what’s going on and sparked a police probe.

There’s no threat to the public and officers have scoured the sewer system to make sure “nothing nefarious had been left behind,” a law enforcement source said.

Since May 5, at least three of the unexplained sewer incidents have been recorded in Brooklyn and Queens.

Investigation follows circulation of videos showing groups climbing out of sewer systems across the city at night

A series of bizarre sightings of people popping in and out of New York’s vast, subterranean sewer system in recent days has the whole city wondering what exactly is going on.

Security cameras have recorded at least three night time instances where groups of people entered or exited sewer tunnels via maintenance holes on streets in Brooklyn and Queens.

Mole people? Mario brothers? Ninja turtles? Bizarre sightings of people entering ad leaving the city’s vast sewer system has left residents wondering what’s going on and sparked a…