Investigators say the suspect attacked a Nassau County Sheriff's Office Correction officer guarding a prisoner at the hospital.
The officer was wounded in the neck, but he is going to be okay, officials say. He required stitches, but he will go home from the hospital Wednesday.
For a few hours any car that left Nassau University Medical Center was searched and the driver questioned.
Police were still trying to track down the person who slashed a corrections officer in the back of the neck as he was sitting watch outside a prisoner's room.
"The subject came up behind him," Nassau County Police Chief Steven Skrynecki said. "He reported that he felt a burning sensation behind the ear."
The officer suffered a large gash, but is ok.
Police went floor by floor through 19th floors looking for the suspect, but to no avail.
"We're reviewing volumes of video. There's an enormous video system here at the hospital so we are methodically going through all the video looking at all the staircases, elevators, floors," Skrynecki said.
Hospital operations thankfully were not affected.
"There has not been any real interruption to any of the patient care. There was some questioning of persons leaving if they had any information to tell officers at the door," Nassau County Police Officer Victor Politi said.
Authorities say they don't believe there is connection between the prisoner and the suspect. They think the suspect has fled the area.