Health care giant Johnson & Johnson says it’s under investigation by federal prosecutors over the company’s practices in marketing a line of hip replacements recalled two years ago because many failed and had to be replaced within five years.

The U.S. Attorney’s Office in Massachusetts and the Civil Division of the U.S. Justice Department last August sent a Johnson & Johnson subsidiary an informal request for information about its ASR XL hip replacements.

J&J says in a regulatory filing that its DePuy Synthes Inc. subsidiary, which makes joint replacements, surgical trauma equipment and other orthopedic surgery products, is cooperating fully with the investigation.

The company says that subsidiary and two others have turned over documents requested by the government.

J&J recalled the DePuy ASR artificial hips in August 2010.