Thieves stealing navigation lights at the Port of Fremantle's Inner Harbour are putting ships and smaller vessels at risk, and are also creating an electrical hazard for the public.

Fremantle Ports Harbour Master Captain Eric Atkinson said the red and green navigational lights mounted on the rocks at the entrance to Rous Head were being stolen and he has asked people using the area to keep a lookout for suspicious activities.

These lights are bolted down inside a heavy metal container and would take some time to steal, Captain Atkinson said.

Not only is there a potential risk to the ferry operators and all other boat users, but these thieves are leaving bare electrical wires which become live at night when our navigation lights are switched on.

We are concerned about the potential risks to vessels and people.

We have replaced four lights already, but it could take just one un-noticed theft to cause a tragedy.

We are seeking the help of the public to please inform the police immediately if you see people interfering with these lights.

Fremantle Ports has installed high-quality locks on the housings of the lights to make them more difficult to steal.

Media contact: Ainslie de Vos 9430 3380