In the wake of a scandal involving the generic drug industry, the Food and Drug Administration announced steps aimed at ensuring the validity of quality-control testing.

The agency said Wednesday it was immediately requiring all laboratories that test generic drugs to make sure they are equivalent to brand name drugs to keep samples of all drugs they test for five years so the FDA can check the tests.Manufacturers of generic drugs must compare their drugs to brand-name drugs to get FDA approval to sell their products. The tests can be conducted by the companies themselves or by outside laboratories.

"The requirement is one of the changes being made because of findings last year and this year that several generic drug firms submitted false information to the agency, in apparent efforts to ensure or speed approvals to market prescription generic drugs," the FDA said.

"In some of these cases, generic drug companies substituted the brand name drug for their own in bioequivalence tests. This meant the tests were comparing the brand-name product to itself, instead of the product to be approved, so that the tests were meaningless and fraudulent," it said.

The new policy "would be a deterrent against this and other frauds, such as switching lot numbers or altering sample identifications," the FDA said.

In addition, "the retained samples can be used as evidence in investigations into wrongdoing," the FDA said.

After discovering the false tests, the FDA analyzed more than 3,000 samples of drugs on the market and inspections at 36 firms that make generic drugs, the agency said.