WASHINGTON, July 18 (Reuters) - U.S. regulators sent a warning to drug maker Watson Pharmaceuticals Inc. (WPI.N: Quote, Profile, Research) last month for failing to fix manufacturing problems at a Puerto Rico plant, a letter released on Tuesday said. An inspection in November and December 2005 found employees failed to handle materials properly to prevent contamination during production of generic antibiotic clindamycin, the Food and Drug Administration said in the letter.
