The US Department of Justice is investigating a number of participants in the Federal Communications Commission’s Personal Communications Services auctions which have been held over the last two and a half years, as companies have allegedly colluded not to compete for certain licenses, according to Reuters. The auction system was designed to stop anti-competitive practices, but companies allegedly used bid signaling to stop others bidding. The auctions have so far raised over $10bn, with further radio auctions taking place around the end of the year. Various companies have been subpoenaed, including AT&T Corp, which declined to comment.