State Police detained a salesman for iRobot Corp. on an inbound flight to Logan International Airport Saturday afternoon after he left replica C-4 plastic explosives in a rental car in Newark, N.J., authorities said.

Employees at a Budget rental car station near Newark Liberty International Airport found two suitcases marked “C-4” during a post-return inspection of a vehicle Saturday, said State Police spokesman David Procopio. He said the employees then took both pieces of luggage into a manager’s office, opened one suitcase, and saw material marked “C-4” with a detonation cord.

They alerted authorities and bomb squads were called to the scene, Procopio said.

Al Della Fave, a spokesman for the Port Authority of New York and New Jersey, said officials there shut down an area of about a few blocks around the rental car facility, which he said is not on the site of the airport.

Massachusetts state troopers waited to question the 33-year-old Somerville man in Boston, where his United Airlines flight was scheduled to land around 4 p.m., Procopio said. They determined that the models were not explosive.

“The investigation revealed that the man is a salesperson for iRobot in Bedford and that he left the suitcases behind by mistake,” Procopio wrote in an email. “The man was returning from a training and sales seminar at Picatinny Arsenal in Rockaway, N.J.”

The arsenal is a facility that provides services and products such as ammunition to all branches of the military, according to its website. iRobot produces and sells several devices, including bomb disposal robots.

Procopio said trained dogs examined all luggage on the plane, and the investigation was ongoing late Saturday afternoon. The man did not appear to be a threat, Procopio said, and his name was withheld because he had not been charged with a crime.