WASHINGTON - Congressional investigators said Tuesday that Medicare had paid tens of millions of dollars to suppliers improperly using identification numbers of doctors who died years ago.

The government has no reliable way to spot claims linked to dead doctors, many of whom are still listed as active Medicare providers though they died 10 or 15 years ago, the Senate Permanent Subcommittee on Investigations said.

Medicare covers wheelchairs, walkers, home oxygen equipment and many other types of medical equipment. When suppliers file claims for equipment provided to a Medicare beneficiary, they normally must list an identification number for the doctor who prescribed or ordered it.

"From 2000 to 2007, Medicare paid 478,500 claims containing identification numbers that were assigned to deceased physicians," the subcommittee said in a new report. "The total amount paid for these claims is estimated to be between $60 million and $92 million. These claims contained identification numbers for an estimated 16,548 to 18,240 deceased physicians."

The subcommittee will hold a hearing on the issue on today.