Thai police on Monday discovered a large cache—more than four tons—of bomb-making materials in a warehouse south of Bangkok rented by a man with alleged links to Hizbullah. The materials—urea-based fertilizer and ammonium nitrate—were found after some 200 police officers raided a three-story building in Samut Sakhon, to which authorities were directed by Atris Hussein, a Swedish-Lebanese man arrested last Thursday following a tip by Israeli authorities who warned of a potential terrorist attack in Thailand's capital against American and Israeli citizens or property. Hussein, who remains in police custody, reportedly told police that the cache was not intended for any attack, but that he intended to ship the materials to another location. It was not immediately clear what the destination was. Police said he had rented the building for more than a year. The U.S. Embassy in Bangkok issued a terrorist warning for American citizens last week, following the reported threat. The warning, Hussein's arrest, and now the cache discovery are unnerving for Thailand, where tourism is a key component of the economy, and which is only now recovering from massive floods last year and social unrest dating back to 2008, including a bloody crackdown by the Royal Thai Army on so-called Red Shirt protesters in 2010 that resulted in the deaths of about 90 people. The U.S. Embassy reportedly has declined a Thai government request to lift its warning to American citizens.