It wasn’t semen after all.

A female Bronx cop claimed that a fellow officer put semen in her half-filled water bottle at their station house, but sources say tests show it wasn’t the bodily fluid — and may have been just mold.

A lab test came back Monday and concluded that there was no semen in the water, law enforcement sources told The Post on Tuesday.

Officer Yesenia Maida, 44, had said she left the water bottle on her desk at the 52nd Precinct station house in Norwood on Nov. 14 and about two weeks later, she found the sticky substance inside the bottle.

Maida reported the incident to her bosses.

Now, sources say, the substance that the cop had discovered in the water bottle may have simply been mold.