The NYPD asked for the public’s help Thursday in solving the mystery behind two young women whose bodies, duct- taped belly-to-belly, washed up in an Upper West Side park.

Cops don’t know their identities — and guessed their ages at 16 to 18, “give or take four years.”

They released sketches of the women, who look alike and were wearing similar clothing, and were fielding tips about what may have happened to them.

The leading theory is that they bound themselves together, taped their own feet and somehow threw themselves in the Hudson River in a suicide pact, sources said.

They may have been romantically involved, since they were found facing each other, the sources said.

A passerby found them in Riverside Park South at West 68th Street around 2:40 p.m. Wednesday, below a pier near a busy jogging and biking path, officials said.

“There was duct tape around the waist that was connecting the two girls essentially,” NYPD Chief of Detectives Dermot Shea said Thursday.

Shea noted that the bodies could have shifted position while in the water.

There were no visible signs of trauma, and the bodies “were not in the water that long,” Shea said.

Based on the tides and where they were found, cops believe the women may have entered the water near the George Washington Bridge and floated roughly 110 blocks south, sources said.

The victims were fully clothed, wearing black, fur-trimmed jackets and black leggings, officials said.

They are the same height, with a similar build, skin tone and hair styles.

NYPD composite sketches, however, suggest that one had a rounder face and the other a broader nose.

“There are similarities in the appearance,” Shea said. “I would describe them as potentially female Hispanic.”

Police are sifting through missing-persons reports to try and find a match.

“That is the priority — identifying these girls,” Shea said.

NYPD Crime Stoppers tweeted an image of sketches side-by-side offering a $2,500 reward for information about the women.

Shea said cops have gotten four tips so far and are following up on each one.

“The most important thing I’ll stress here for everyone is get the word out — we put out pictures, composite sketches, of these two women,” he said.

The Office of Chief Medical Examiner is working to determine a cause of death, but the agency said in a statement late Thursday that it “requires additional analysis” before it can come to any conclusions.

“We’re working very closely with the Office of Chief Medical Examiner to determine the cause of death,” Shea said.

“Our hearts go out to the families.”

Additional reporting by Cedar Attanasio