Two unidentified men were found dead under mysterious circumstances Saturday morning in Manhattan and Staten Island, authorities said.

Around 2:25 a.m., an unresponsive man was found lying on his back outside the Mike Weiss art gallery on West 24th Street near Tenth Avenue in Chelsea, cops said.

The man, whom police sources said was not carrying identification, was pronounced dead at Lenox Hill Hospital.

Sources said the man’s body displayed no immediately apparent signs of trauma.

Four hours later, a man’s severely decomposed body was spotted bobbing in the water off Staten Island’s Fox Beach, police said.

A police source said the corpse found near Kissam Avenue and Mill Road appeared to have been exposed to the elements for some time.

It was impossible to quickly tell if the waterlogged body had signs of trauma due to the extent of the decomposition, the source added.

The medical examiner’s office is working to determine how both men died.