A YOUNG chemistry student working as a volunteer to prepare a visit by the Pope to Madrid has been arrested on suspicion of planning a gas attack targeting protesters opposed to the pontiff's stay.
More than a million people are expected to greet Pope Benedict when he arrives today for a four-day visit to celebrate World Youth Day. The celebrations started on Tuesday.
Police said the suspect arrested in the capital on Tuesday is a 24-year-old Mexican student specialising in organic chemistry.
He was arrested at a Madrid convention centre where the hundreds of thousands of pilgrims are supposed to pick up their accreditation, a police official said.
An unnamed official with the visit's organising committee said the Mexican was a volunteer working to help deal with the massive flow of people coming to Madrid.
A total of 30,000 people from around the world are taking part in that organising effort, with 10,000 police providing security.
The Mexican Embassy identified the detainee as Jose Perez Bautista.
A court official said he would appear before a judge today at the earliest.
The official said he had been making threats over the internet against people in Spain opposed to the Pope's visit.
Police said that officers who searched the detainee's apartment in a wealthy district of Madrid seized an external hard-drive and two notebooks with chemical equations that had nothing to do with his studies.
They said he tried to recruit people via the internet to help him, and that a computer allegedly used for this purpose was among objects seized by police.
The man had planned to attack anti-Pope protesters with "suffocating gases" and other chemicals, the police statement said. But it did not mention confiscation of chemicals that could be used in an attack.
Without knowing what chemicals and delivery system the man may have had, it is impossible to know what harm he could have caused to angry protesters marching through the streets of Madrid last evening, said Magnus Ranstorp, a terrorism expert at the Swedish National Defence College in Stockholm.
The suspect was in Madrid studying with Spain's top government research body, the Spanish National Research Council.
Mexico's Autonomous University of Puebla confirmed that a man with the same name had completed an undergraduate degree in chemistry in 2009.
Church organisers say the papal visit is costing about €50 million to stage.
Protesters complain the government is essentially spending taxpayers' money on the visit by granting tax breaks to corporate sponsors and perks such as discount subway and bus tickets for pilgrims.