Police investigate men who entered and exited Brooklyn sewers in dead of night

New York City police are investigating a series of puzzling incidents in which groups of men were spotted emerging from sewers across Brooklyn — behaviour that has left authorities and residents baffled.

The New York Police Department confirmed in a statement to PEOPLE that the activity poses no threat to the public.

Officials have speculated that the individuals may have been "scouring the system for valuables that get into the sewage," according to an NYPD official, as reported by NBC News.

Two separate incidents on the same night

The NYPD said at least seven people used a manhole to access the sewer network near McDonald Avenue and Colin Place in the Gravesend neighbourhood on the evening of Sunday.

The group descended into the sewer at around 11pm and resurfaced onto the street at approximately 2am on Monday.

Later that same night, at around 1am, a separate group of eight people entered the sewer system near Heyward Street and Bedford Avenue.

That group emerged at 3:40am, before fleeing the scene in a car to an unknown location, according to police.

Authorities declare area safe

The NYPD and the New York City Environmental Protection Department (NYC DEP) attended both scenes and confirmed the areas were "safe and free of hazards," as stated by the NYPD's 62nd Precinct in an X post.

Following its inspection, NYC DEP also confirmed it had "found no damage to the sewer system equipment," per NBC News.

Potential burglary charges despite no arrests

Despite no damage having been reported, entering a sewer system is illegal under New York law. No arrests have been made at this stage, though police indicated that those responsible could face burglary charges.