One of the Vatican's main Twitter accounts and the website of its communications office were running stories about Batman on Thursday with the headline "Holy Switcheroo!" - raising concerns they might have been hacked.

But two Vatican officials said the site hadn't been hacked, and that the reason for the unusual posting was an "internal system failure" due to a non-native English speaker posting the story on the website.

The story was from the Catholic News Service. It has as its headline: "Holy Switcheroo! Batman has grown bitter, more vengeful with the years" and details the evolution of the Batman comic franchise.

"Admittedly some people might have been thrown off by the headline," said Greg Burke, a Vatican communications adviser.

Monsignor Paul Tighe, the No. 2 in the Vatican's social communications office, said the office's website, www.pccs.va runs stories about communications issues and regularly takes copy from Catholic News Service, the news agency of the U.S. Conference of Catholic Bishops.

Once a story is posted, he explained, it generates an automatic tweet on the office's Twitter handle (at)pccs-va.

"I thought we had been hacked to be honest," he said. But further investigation yielded a simpler explanation. The story was later lowered down from the lead story on the site.

The other stories on the website are much more church-oriented in nature. On Thursday, they included Pope Francis' explanation of how he decided on calling himself Francis, the address to the media by the head of the social communications office about coverage of the papal conclave, and a story about registration being open for a congress on the role of the media in promoting peace.

Earlier this week, the Twitter account of a senior Vatican official was hacked.