A top U.S. senator has asked federal housing officials to make a deeper probe into a troubled Massachusetts housing authority, where top managers are allowed to live in subsidized housing while hundreds of low-income families languish on waiting lists.

Iowa Republican Charles Grassley, who has already launched an investigation into the $360,000 salary paid to former Chelsea Housing Authority Director Michael McLaughlin, is demanding a full explanation of why authority employees making $50,000 a year live in public housing for $25 in monthly rent.

McLaughlin has since resigned.

The Boston Globe reported that Grassley expressed his concerns in a Feb. 6 letter to Housing and Urban Development Secretary Shaun Donovan.

The housing authority in Chelsea, just north of Boston, gets about $10 million a year in federal money. (AP)