By David Barboza 

SHANGHAI: China is investigating whether companies here are providing and shipping raw materials to factories producing illegal steroids in the United States.

The government said over the weekend that it was cooperating with the U.S. authorities, who last week announced the largest crackdown ever on steroid production facilities in the United States and other parts of the world.

American authorities have said that 99 percent of all materials used to produce anabolic steroids in the United States come from China.

The U.S. Drug Enforcement Administration and other enforcement bodies in the United States announced the arrests of over 120 people last week and said they had closed dozens of small laboratories in the country, seizing cash, drugs and other assets.

The DEA did not disclose who used the steroids but said it had a large database of names and believed that many of the users were bodybuilders and other athletes.

U.S. officials said 37 Chinese companies were involved in the illegal trade and that they had turned over the names of most of the companies to the Chinese authorities.

Only one Chinese company was named by the investigators, GeneScience Pharmaceutical, which is China's largest producer of human growth hormone.

In mid-September, a Rhode Island grand jury indicted GeneScience and its American-educated founder and chief executive, Jin Lei.

The U.S. authorities accused GeneScience and its founder of supplying human growth hormone to distributors in the United States, where it is not licensed to be sold. Investigators in the United States said that GeneScience sometimes mislabeled drugs it shipped as toys, glassware or hair products.

GeneScience officials did not return phone calls seeking comment last week.

But a spokesman for the parent company of GeneScience, which is based in the north China city of Changchun, said the Chinese government had not yet contacted the pharmaceutical company.

Zhou Weiqun, board secretary of GeneScience's parent company Changchun High Tech Group, said the company had learned about the indictment from investors who had read press reports.

China's state-controlled news media did not carry many reports of the steroids crackdown in the United States, but foreign media reports circulated inside the country and over the Internet.

The Chinese government's first response came over the weekend, when a spokesman for China's State Food and Drug Administration, told Xinhua, the official Chinese press agency, that the authorities were cooperating with U.S. officials and that regulators will take action against any illegal activities.

"We will find out the truth as soon as possible and if there are illegal activities, we will handle them at once, according to the law," said Yan Jiangying, an agency spokeswoman.

The Chinese regulator said the government had strict controls over the use of steroids and that no individual or organization is allowed to produce or sell steroids without a license.

There was no mention of human growth hormone or other illicit drugs named by U.S. investigators.