Anti-corruption officials are calling for Peru’s three most recent ex-presidents to testify in connection with alleged bribes paid by Brazilian construction conglomerate Odebrecht for inflated contracts that authorities say cost the Andean country $283 million.

Comptroller Edgar Alarcon said at a news conference Wednesday that Odebrecht was involved in 23 public works projects since 1998 worth at least $16.9 billion. Of those, 16 have been audited and authorities detected potential irregularities, including unjustified cost overruns and forgiveness of penalties for contractual breaches that cost around $283 million.