The Times (p19) reports that land deals worth£60m are being investigated by South Yorkshire Police's commercial branch in Doncaster.
Councillors and officials are accused of accepting favours for approving developments around the town, sometimes in contravention of their own green-belt policy.
The inquiry is part of Operation Danum, launched almost three years ago. It has so far cost the public purse£1m and is expected to continue for at least the next six months and probably considerably longer.
Some trials are pending and detectives are checking council expense forms with hotels and organisations that stage conferences attended by councillors and officers.
However, officers are also looking at suspicious planning applications and land deals. They allegedly involve planning permission for housing developments, misuse of grants for improvements to homes and contract fiddles.