Federal regulators say Teva Pharmaceutical Industries Ltd.'s Parenteral Medicines unit failed to correct manufacturing problems at its Irvine, Calif., facility that caused contamination in batches of an anesthetic.

The Food and Drug Administration sent the Israeli generic drug developer a warning letter in December citing contamination with batches of pharmaceuticals made at the facility. The letter was posted Tuesday on the agency's Web site.

Teva says it has moved its yearly plant shutdown to the last week in April from December "in order to more efficiently address process enhancements at the facility."

The company says it continues to work with the FDA to address any concerns.