A man sexually assaulted a 4-year-old girl in the play area of a McDonald’s in Queens and investigators are trying to determine whether it’s the same suspect who reportedly molested a 9-year-old girl a few months ago, authorities said.

An unidentified pre-schooler crawled up a tube to get to a slide inside the Hillside Avenue restaurant in Jamaica at 8:25 p.m., Tuesday, when she encountered a creep who had been lying in wait, law enforcement sources said.

The man forced the girl to perform oral sex until she fled down the slide and told her mom what happened, sources added. The engraged and distraught mother begged a security guard for help but he did nothing as the suspect tried to flee out an emerency exit, sources said.

The exit was locked, forcing the suspect to turn and head toward the front door and the mother managed to grab him, sources added. The suspect managed to wriggle out of her grasp and escape — again while the security officer stood by and did nothing, the mother complained to police.

Video showed a man walk into the fast-food joint around 6:45 p.m. and head for the play area where he hid until the child encountered him and he ran off around 8:25 p.m., sources said. Despite that, the security guard told cops he saw nothing and questioned the mother’s credibility, sources said.

Police believe an assault occurred and are looking into whether it’s related to an attack on a nine-year-old girl around 3:30 p.m., March 9, sources added. In that instance, a man waited in the same spot and asked the child to sit on his lap and play a video game, sources said. He rubbed the child’s buttocks while telling her she was beautiful, sources added.

The suspect is described as being in his late teens or his 20s and was last seen wearing a brown or dark purple short-sleeved Polo shirt, jeans and white sneakers, police said. He also has a lump or bandage on his forehead.

Anyone with information is asked to call Crime Stoppers at 1(800) 577-TIPS.

kconley@nypost.com