THE cause of a fire that continues to tear through Wentworth's Junction Island is yet to be determined.

Fire and Rescue NSW said the fire started about 1.30pm on Saturday and is expected to burn for several days due to the island's large gum trees and heavy undergrowth.

Fire and Rescue NSW Wentworth brigade attended the blaze, supported by NSW Rural Fire Service and Country Fire Authority brigades from Merbein and Mildura, as well as a fire boat from Parks Victoria.

"We certainly don't know if it's suspicious yet, purely because it started on the western tip of the island, which we've been unable to access because of the large amount of gumtrees alight which are dropping limbs and making the area unsafe," Fire and Rescue NSW Wentworth captain Corey Bysouth said.

"At least 600 metres of the island has been burnt out on the western end and we've got a containment line in to stop it spreading any further," he said.

"It is contained at the moment, but it will continue to burn for several days as you just cannot put those large gumtrees out."

Mr Bysouth said while no property was destroyed and there were no injuries, residents fronting the river along Cadell Street should stay alert.

"Those residents need to remain vigilant for any embers that land on their property," he said.

"The wind on Saturday played a big role -- it was quite strong and coming from the south west, which did cause a couple of spot fires across the river in people's private property.

"The crews from the RFS and the CFA were over that side purely for property protection in case of any ember attack and I believe they did extinguish a couple of spot fires."

Mr Bysouth said Fire and Rescue NSW crews continued to monitor the fire until about midnight on Saturday and were redeployed at first light on Sunday.

"The island is shut to the public, so if people can stay away from that area, the crews from Fire and Rescue will be monitoring the fire over the coming days."

Anyone with details about how the fire started are urged to call Dareton Police on 5027 7599 or Crime Stoppers on 1800 333 000.