Pope Francis yesterday said he had personally ordered an investigation into a case of sexual abuse of a minor by priests in Spain because he felt the Church should not hide the truth.

Three Spanish Catholic priests and a lay person were arrested in Granada on Monday. The case emerged after a man wrote to the Pope telling him of how he had been molested when he was an altar boy.

“I read it. I called the person and I told him ‘go to the bishop tomorrow’ and then I wrote to the bishop and told him to start an investigation,” Francis said in response to a question by a Spanish reporter on his plane from Strasbourg, France, where he had addressed the European Parliament.

“I received this news with great pain, very great pain, but the truth is the truth and we should not hide it.”

It was not clear when the man had written to the Pope. Investigations into the case in the southern province of Granada started “some time ago”, Interior Minister Jorge Fernandez Diaz told reporters, without giving further details.

Pope Francis has promised a policy of zero tolerance for sexual abuse of minors by clerics, after Church scandals in several countries over many years, but groups representing victims say he has not done enough.

The Vatican said earlier this year that between 2004 and 2013, it had defrocked about 850 priests who had been accused of sexual abuse of minors.