The FBI is probing into how a stun gun disguised as a cell phone ended up on a flight from Boston to Newark, New Jersey on Friday.

All 96 passengers had deboarded JetBlue flight 1179 at Newark Liberty International Airport when a cleaning crew discovered the object in the seatback pocket at around 10:30 p.m. according to a JetBlue spokesman.

The next flight was delayed by approximately 30 minutes as a K-9 unit checked for other contraband.

The weapon was handed over to police from the Port Authority of New York and New Jersey, and the investigation was taken over by the FBI, the Transportation Security Administration said in a statement.

All current information indicates this is not part of an attack, said Special Agent Bryan Travers of the Newark Division of the FBI.  He added that the FBI has identified the passenger who was sitting in the seat that uses the pocket in question, but could not yet link that person to the stun gun definitively.

Police described the gun as looking like a cell phone, a Port Authority spokesman said.  Cell phone stun guns are designed to closely resemble smartphones and are advertised as covert self-defense items.

Officials at Massachusetts Port Authority, which owns and operates Logan International Airport, had no comment on the incident.

It was unknown whether the device was sneaked past security, was placed on the plane after it landed, or belonged to a law-enforcement official, a U.S. source familiar with the investigation told Reuters, requesting anonymity.

Flights used in the September 11th terrorist attacks orginated from both Logan and Newark.