South Carolina's inspector general is launching an investigation into whether people with disabilities have been overcharged for their care, he said Tuesday.

Patrick Maley told The Associated Press he has no timeline on his investigation but aims to report his findings as soon as possible for the sake of potential victims.

His inquiry comes after a former commissioner for the state Department of Disabilities and Special Needs went public with allegations that several of the agency's providers were incorrectly charging disabled clients for rent in group homes. Some are not properly crediting federal housing subsidies that are supposed to offset room and board costs for eligible residents, Deborah McPherson said.

She said she decided to speak up several months after taking her concerns to the agency's director.

"I felt the only way for this to be corrected was to make it public," said McPherson, whose five-year tenure on the board ended in May. "That money can make a big difference in their quality of life."

Agency spokeswoman Lois Park Mole said the agency has been working to correct any potential problem, starting with a memo to providers in late May clarifying how clients should be charged. The agency is hiring an outside accounting firm to review how local disability boards are applying the subsidies, which they receive directly from the U.S. Department Housing and Urban Development.

Providers are supposed to apply the subsidies toward clients' room and board before calculating what they owe in rent and utilities. Those payments come out of their income, which can include Social Security payments and a job arranged through the disability board.

The agency's review will start with billings in July 2012. A second review could go back further, if necessary, Mole said Tuesday.

After McPherson raised the issue, the agency met with a sampling of providers and learned they're "using different methods to calculate the room and board charge," but that doesn't necessarily mean they're doing it incorrectly, Mole said.

Residents will be reimbursed for any overpayments identified by the agency's review, she said.

The extent of the potential overbillings is unknown.