WINDSOR, Ont. -- A Canada-wide arrest warrant has been issued for the Vatican diplomat who was recalled from the United States in a child pornography investigation, accusing him of accessing porn over Christmas last year from a church.

Police in Windsor, Ont., said Carlo Capella, a 50-year-old monsignor from Italy, allegedly uploaded the child porn to a social networking site while visiting a place of worship in Windsor between Dec. 24 and Dec. 27.

The Vatican recalled Capella, the No. 4 official in its Washington embassy, after the U.S. State Department notified it Aug. 21 of a "possible violation of laws relating to child pornography images" by one of its diplomats in Washington.

It never identified Capella by name and provided no details of the accusations, sparking criticism from U.S. church officials who have been under fire for decades of coverups of priestly sex abusers.

Windsor police provided the most information about the case in a statement Thursday announcing the arrest warrant, and the archdiocese of London, Ontario, confirmed it had assisted authorities in the investigation of "Msgr. Capella."

In the statement, Windsor police accused Capella of accessing, possessing and distributing child pornography. It said authorities were alerted in February that someone in Windsor had allegedly uploaded child porn using a social networking site.

They obtained records of the internet service provider and determined the dates in question. It said it had issued a Canada-wide arrest warrant for Capella, though it noted that he had returned to Italy.

Capella is currently in Vatican City, though the Vatican hasn't said under what terms.

Canadian police declined to say if they had passed the case to Interpol or if Canada would initiate extradition proceedings. The Vatican doesn't extradite its citizens, however.

In explaining its decision to recall the diplomat, as is common in such cases, the Vatican said its own criminal prosecutors were now investigating the case and seeking information from the U.S.

At the time of the Sept. 15 announcement about Capella's recall, neither the Vatican nor the State Department made any mention of a Canadian angle to the case.

Capella was a high-ranking priest in the Vatican's diplomatic corps. He served on the Italy desk in the Vatican's secretariat of state and was part of the official delegation that negotiated a tax treaty with Italy before being posted to the U.S. embassy last year.

A canon lawyer, Capella is listed online as having written a 2003 paper for the Pontifical Lateran University on priestly celibacy and the church's criminal code.

Several U.S. church officials have complained that the Vatican was being less than transparent about the case.

The head of the U.S. Conference of Catholic Bishops, Cardinal Daniel N. DiNardo, urged the Holy See to be "forthcoming with more details" about the case, a reflection of how the U.S. church still struggles with credibility problems 15 years after the sex abuse scandal erupted in the U.S.

The diplomat's recall was expected to loom over an international conference next week at the Pontifical Gregorian University in Rome on protecting children from online sexual exploitation, pornography and abuse.

Cardinal Pietro Parolin, the Vatican secretary of state and Capella's boss, is to deliver the keynote speech Tuesday on "The Holy See and its commitment to combating sex abuse online."

Panelists at the conference, which was organized months ago, are to include top law enforcement and academic experts in the field of child protection and cybercrimes.