NEWARK, N.J. (AP) _ Two Virginia Military Institute cadets on Christmas vacation robbed an armored car of $4.5 million in a plan conceived by one cadet's father, authorities said Wednesday in announcing their arrests.

The father, Robert J. Jasinski, 51, of Boonton was a part-time driver for the Coin Depot Armored Car Corp. of Elizabeth when one of its trucks was robbed Dec. 22 in Clifton by two men dressed as police officers.

The two ''policemen'' were William T. Jasinski, 22, and Bryan Smals, 21, of Columbus, Ohio, cadets at the Lexington, Va., miltary school, said John McGinley, head of the FBI's Newark agency.

The elder Jasinski met the hijacked armored car in a rented van, to which the money was transferred; the police uniforms were rented from a costume store in Paramus, McGinley said at a news conference.

A ''majority'' of the money was recovered from an attic crawl space at the home of a woman acquaintance of the elder Jasinski, McGinley said. The woman, whom he did not identify, did not know what Jasinski was storing and did not participate in the crime, McGinley said.

The money, displayed with a 9mm automatic, was in a dozen plastic garbage bags and a footlocker.

McGinley said the cadets were arrested at their campus Wednesday. Robert Jasinski, a retired telephone company worker, was arrested at his home and held on $400,000 bail.

The lawyer who represented the elder Jasinski, Edward Hartnett, declined to comment on the charges.

All three were charged with interference with commerce by threats or violence, which carries a 20-year prison term upon conviction.

William Jasinski, a senior, and Smals, a sophomore, were friends on vacation from the military school when the crime was committed, said McGinley.

The complaint said Robert J. Jasinski was interviewed by an FBI agent on Tuesday and at first denied the allegation. He later admitted planning the robbery and implicated the cadets, the complaint said.

In Roanoke, Va., Wednesday night, U.S. Magistrate Glen Conrad ordered the younger Jasinski and Smals held without bond pending their transfer to Newark.

FBI agent Frank Butler said Jasinski and Smals confessed to the heist when they were questioned at VMI following their arrests, and both cadets also admitted their guilt at the bond hearing.

''The complaint is correct, sir,'' Jasinski told Conrad at the hearing.

McGinley said an investigation of employees after the robbery was ''instrumental'' in cracking the case. He said Jasinski drove the same route as the robbed truck.

Authorities said the two robbers held up three employees of Coin Depot as they parked an armored car behind the First Fidelity Bank. The car was to bring the cash to the Federal Reserve Bank of New York.

They handcuffed the employees and drove them to a nearby industrial park, freeing the three unharmed.

The FBI said the robbers wore police-type clothing, including three-quarter length blue nylon coats with fur collars, blue police caps and police badges.