Seven people have been arrested in connection with a missing £10.25m loan to Northampton Town Football Club.
A statement from Northamptonshire Police said it was investigating "allegations of theft and fraud, bribery, misconduct in public office and electoral offences".
The Northampton Borough Council loan was made in 2013 to redevelop the Sixfields stadium.
Nine other people have also been interviewed under caution, police said.
Detectives would not be drawn on the "nature of the interviews or the identity of those interviewed", Thursday's statement said.
The police statement also revealed detectives were analysing the "results of thousands of financial transactions" and following "700 lines of inquiry".
It added: "To date, this has resulted in over 500 statements and reports being produced and more than 2,100 exhibits being seized.
"This investigation has resulted in the arrest of seven individuals from across the country, with a further nine interviewed at length under caution."
The row began when the loan was first agreed in the summer of 2013. A police inquiry into "alleged financial irregularities" surrounding the money was launched in November 2015.
Meanwhile, work on Northampton Town's East Stand redevelopment at Sixfields Stadium remains incomplete.