PARIS  The French authorities have arrested a physicist who worked for years at CERN, the huge nuclear research center in Switzerland, on suspicion of links to Al Qaeda’s affiliate in North Africa, the center said Friday.

James Gillies, a CERN spokesman, said the physicist was still registered as a member of the research team but had not been seen for some time. In a statement, the center said that he was arrested Thursday and had worked as an analyst on projects involving its Large Hadron Collider, the world’s largest particle accelerator, since 2003, but that he was not an employee.

“His work did not bring him into contact with anything that could be used for terrorism,” said the statement from the center, whose formal name is the European Organization for Nuclear Research. “None of our research has potential for military application, and all our results are published openly in the public domain.”

A person with knowledge of the investigation said that the physicist was arrested along with a younger brother, but that the physicist was the focus of the investigation. Both are French citizens of Algerian origin.