Blue and white helicopter flying against blue sky

The Westpac Rescue Helicopter is involved in the search. (ABC News: Mackenzie Heard)

A search is underway for an overdue vessel with four people on board off Tasmania’s north-west coast, near Robbins Island.

Tasmania Police said four people left on a fishing trip yesterday, but had not returned to the campground at Montagu.

Concerned relatives raised the alarm in a call to police just after 8 am today.

The vessel left the Montagu boat ramp at 5:30 pm yesterday, with the four people on board, police said.

The Westpac Rescue Helicopter and marine rescue vessels have been deployed to the area.

A police boat moving across water.

Tasmania Police’s boat Van Diemen was tasked to help investigate a flare being sighted. (Tasmania Police)

Police are also seeking information after a distress flare was sighted off Flinders Island on Saturday night.

Police said a member of the public reported seeing the flare off the western side of the island, near Prime Seal Island, about 8:15 pm.

Due to the report, the rescue helicopter and police vessel Van Diemen were dispatched to the area.

They carried out a search, but were unable to find any vessels or signs of distress.

When asked if the flare sighting could be related to the overdue boat, Tasmania Police said it is “not discounted” but is “likely too far from Robbins Island” to be related.