Police have launched an investigation after a video recently spread showing men in work clothes emerging one after another from a manhole in the middle of Manhattan, New York.

Recently, a video was uploaded to social media showing three men wearing coveralls and headlamps on their foreheads coming out of a manhole on a New York street while looking around.

In New York, people in similar attire were previously spotted coming out of sewers in Queens and Brooklyn last May, prompting police to conduct a search.

It has been suggested that they might be a type of "treasure hunter" searching the sewer system for valuables. It has not yet been confirmed whether this recent video is related to the incident in May.

(Reported by Yang Hyun-yi | Video by Seo Byeong-wook | Graphics by Lee Su-min | Source: New York Post, Instagram 'ricardyfabre', AKI AUTO CARE) / Produced by SBS Digital News