Archbishop of Granada Francisco Javier Martinez and priests prostrate in front of the altar to seek pardon for sexual abuse in the Church at the cathedral in Granada, southern Spain, November 23, 2014. REUTERS/Pepe Marin

MADRID (Reuters) - Three Spanish Catholic priests and a lay person were arrested on Monday, a police source said, in a child sexual abuse case whose victim Pope Francis has reportedly telephoned to offer the Church’s apology.

Investigations into the case in the southern province of Granada started “some time ago,” Interior Minister Jorge Fernandez Diaz told reporters, confirming four arrests, but he could not give further details because the issue is sub judice.

Granada Archbishop of Granada Francisco Javier Martinez last week removed several priests from their duties after a man wrote to Pope Francis saying he was abused when he was an altar boy.

The Argentine-born pope personally called the man in August to apologize on behalf of the Roman Catholic Church, according to the Spanish religion news website Religion Digital.

The website said the four suspects belonged to an unofficial arch-conservative group of priests and lay Catholics in Granada. The interior ministry statement did not identify them.

On Sunday, the archbishop and six priests prostrated themselves in front of the altar in Granada’s cathedral to seek pardon for sexual abuse in the Church.

“We will cry for a few minutes in silence to God to ask his forgiveness for all the Church’s crimes, for all the scandals there have been and for those that may have taken place among us and anywhere in the world,” Martinez said.