A close ally of former Panamanian President Ricardo Martinelli has been arrested as part of a widening probe into the alleged payment of bribes and kickbacks in the purchase of an Italian-made radar system.

Former Minister of Public Safety Jose Mulino was taken into custody Monday night after being questioned for several hours about the $125 million contract he signed in 2010 for 19 drug-surveillance radars. He has denied any wrongdoing.

Mulino is the fourth cabinet minister from Martinelli’s government to be jailed on corruption charges since the billionaire supermarket magnate’s term ended last year. Six investigations against Martinelli are also slowly working their way through the Supreme Court.

The high court in August canceled the contract with a unit of Italian industrial giant Finmeccanica over corruption concerns.