MADRID (AP).- A priceless collection of 12th-century religious manuscripts was stolen from a cathedral in the northwestern Spanish city of Santiago de Compostela, police said Friday.

Galicia regional police inspector Benigno Roca said a special unit has been set up to try to recover the Calixtinus Codex, which went missing from a strongbox in the cathedral's archive room last week. He said there were no signs of a break-in. Roca said European police forces had been alerted.

Cathedral dean Jose Maria Diaz said the richly-decorated tome was of incalculable value. He said whoever took it knew this and knew where to find it.

"If I suspect anyone I won't say who because it's a sin to make rash accusations," Diaz told reporters.

The codex is considered the first guide for people making the ancient Christian pilgrimage known as the Camino de Santiago, the Spanish name for the Way of St. James.

Francisco Singul, an art historian and expert on the pilgrimage, told Cadena SER radio the theft "was comparable to stealing 'Las Meninas'," in reference to painter Diego Velazquez's masterpiece in Madrid's Prado Museum.

The cathedral's dean said the book was reported missing Wednesday. Police said it is believed to have been taken the previous week.

Speaking to reporters, Diaz said only he and two other people had keys to the room where it was stored.

"The theft of the codex strikes me as disgraceful because it was very important for Santiago, Spain and the world," said Mariano Rajoy, head of Spain's leading conservative Popular Party.

Copyright 2011 The Associated Press.