PROVIDENCE, R.I. – Federal authorities announced the largest crackdown on illegal steroids in the nation’s history yesterday, arresting more than 120 people and raiding dozens of labs that manufactured growth hormone for sale on the black market. Agents seized 56 labs, many of which were located in dirty basements, and recovered 11.4 million doses of steroids, according to the Drug Enforcement Administration. “We were a little bit stunned at the amount of labs we found as a result of this investigation,” DEA spokesman Garrison Courtney said in Washington. “It’s not something that’s on a scale that we’ve ever seen.” The announcement follows a growing number of scandals in the sports world over steroids, but authorities said the probe was focused on distributors, not users, and that no professional athletes were directly involved in the investigation. U.S. investigators were helped by governments of nine other countries, including China, which is hosting the 2008 Olympics.