The U.S. government is investigating two Indian outsourcing firms and a California power company over whether they violated labor and immigration laws by replacing American workers with foreigners on temporary work visas. The Labor Department said it is trying to ensure the Indian companies and Southern California Edison complied with the terms of the nation s skilled-worker-visa system. Controversy has exploded in recent months over whether these foreign workers, who typically have visas known as H-1Bs, displace or complement U.S. workers.