When Minnesota schoolchildren found an outbreak of deformed frogs in the summer of 1995, scientists thought it would be only a matter of months before they figured out the cause. But nearly two years later, it's still a mystery, and the federal Environmental Protection Agency is becoming increasingly concerned. The EPA is preparing to spend several million dollars to investigate the problem, and find out whether it poses a threat not just to frogs, but to humans. Minnesota Public Radio's Mary Losure reports.