A beach scrub fire which crews battled overnight on Thursday may have been deliberately lit and the cause is being investigated.
A helicopter was needed to fight the 2.5 hectare fire along a section of coastline between Castlecliff Beach and Kai Iwi Beach, 4km west of Seafront Rd.
Deputy principal rural fire officer for Whanganui, Gavin Pryce, said the fire spread through beach, sand dunes and scrub "which encapsulated some rather large cliffs".
There were no homes or property in danger and the cause was not yet known.
"But we suspect it was deliberately lit," Mr Pryce said.