The cash-strapped District government will have to come up with as much as $6 million to cover the life insurance premiums the city collected from hundreds of disabled employees over seven years but didn’t pass along to the insurance companies, officials said Tuesday.

Mayor Adrian Fenty and Attorney General Peter Nickles said at a news conference that they had asked the city’s independent inspector general to investigate what happened to the money that had been collected by the city’s Office of Risk Management.