THESSALONIKI (AP) — Authorities have charged the harbor police chief in Greece’s second-largest commercial port of Thessaloniki and another 17 people over alleged graft involving tugboat services to incoming ships.

Police say the suspects include six state-employed harbor pilots, the owners of four tugboat companies and seven company employees. All deny wrongdoing.

Police said Tuesday the arrests followed a complaint by a rival firm that tugboat owners, assisted by corrupt harbor police officials, misled visiting cargo ships into hiring more tugs than were needed to bring them in to port.

As a result, the complaint said, smaller competitors who lacked enough tugs were driven out of business.

Thessaloniki port officials said the crackdown has not hampered harbor operations.

The suspects were arrested Monday in Thessaloniki and Greece’s capital, Athens.