BUENOS AIRES, Argentina (AP) _ A federal judge opened an investigation Tuesday into allegations someone attempted to sabotage the jetliner that was to have carried Italian President Sandro Pertini back to Rome.

Judge Jorge Branca, whose jurisdiction includes Ezeiza International Airport, said the investigation will determine if any criminal actions were involved.

Italy's Alitalia airline issued a communique in Rome saying mechanics conducting a final check of the Alitalia Boeing 747 Monday night found the small metal caps to five of the plane's ten tires were missing.

A statement from the Argentine Defense Ministry said three of the caps were found in one of the jet's turbines, and local and Italian news reports said the two other caps also were found in the engines.

But a report released by the air force, which oversees operations at the airport, claimed none of the caps was found. It said the jumbo jet's engines were tested and found to be running properly, but Alitalia officials decided to accept a substitute Argentine plane which took Pertini to Rome.

The Alitalia communique said the mechanics were convinced the safety caps had been removed deliberately, but a follow-up security check found ''no other anomalies.''

Airline and government officials, including Foreign Minister Dante Caputo, said late Monday only that the plane had ''technical problems.''

Another Boeing 747 was supplied by the Argentine state airline, Aerolineas Argentinas, and Pertini, a Socialist, departed early Tuesday three hours behind schedule.

Shortly after his arrival in Rome, the 88-year-old president boarded another jetliner for the flight to Moscow where he will attend Wednesday's funeral for Soviet President Konstantin Chernenko.

A Rome prosecutor, Silverio Piro, said Tuesday night he also was opening an investigation into the reports of possible sabotage. He said he will summon witnesses and ask for technical documents from Alitalia.