A state institute has opened an investigation into whether communist-era security services in Poland and other former East bloc nations had a role in the 1981 assassination attempt against Pope John Paul II, a spokesman said Tuesday.

John Paul was shot and seriously wounded on May 13, 1981, in St. Peter's Square by Mehmet Ali Agca, a Turk. But it has been suggested that larger political motives may have been behind the attack, because having a Polish-born pope was considered a danger by the Soviet leaders of the time.

"Prosecutors are gathering documents on whether communist services were part of a plot concerning this assassination attempt," Andrzej Arseniuk of the National Remembrance Institute told The Associated Press.

He said the institute has asked Italy's Justice Ministry for files it has on the shooting and is also examining documents gathered by Italian magistrate Ferdinando Imposimato, whose own investigation concluded there was a Soviet link.

Poland's Institute of National Remembrance, which investigates communist and Nazi-era crimes, opened the investigation because the John Paul was a Polish citizen and because communist services seem to have been involved in the shooting, Arseniuk said.

He could not say how long the inquiry could take.

An Italian parliamentary commission concluded earlier this year that the Soviet Union was behind the attack, confirming suspicions that many have held in the past quarter-century.

The commission said the Soviets considered John Paul a danger to the Soviet bloc because of his support for the Solidarity labor movement in his native Poland. Solidarity was the first free trade union in communist Eastern Europe.

Agca served 19 years in an Italian prison for shooting the pope and then 5 1/2 years in Turkey for killing journalist Abdi Ipekci.

He was released from the Turkish prison in January, but returned days later when prosecutors said he must serve more of his 10-year term for killing Ipekci. He is due to be released in 2010.

John Paul II died April 2, 2005, after serving as pope for almost 27 years.