The stern of a stricken cargo ship which ploughed into a reef off New Zealand's coast three months ago is sinking into the ocean, officials say.
They say most of the stern of the Greek-owned Rena - which broke in two at the weekend - has slipped off the reef and is now submerged.
The bow section remains upright and wedged on the reef.
The Rena has leaked large amounts of fuel in what was New Zealand's worst maritime environmental disaster.
"The foremost part of the stern was still sticking up out of the water, with the rest - including the bridge - submerged," Maritime New Zealand said in a statement on Tuesday.
The agency's spokesman James Sygrove described the situation as "fluid", adding that the authorities remained unsure of what would happen next, the Associated Press news agency reports.
Official fear that the sinking of the stern could further complicate salvage efforts.
Some 150 cargo containers with milk powder and timber have spilled into the ocean since the 236-metre (775ft) vessel snapped in two, after being pounded by waves of up to 6m (20ft).
Hundreds of tonnes of fuel have leaked since the Rena ran aground on 5 October, killing thousands of seabirds.
Salvage crews have managed to remove more than 1,100 tonnes of oil from the vessel, but some 100 tonnes remain aboard.
The Rena struck the well-marked Astrolabe Reef off the North Island resort area of Tauranga in October.
Its captain and other senior officers face up to 16 charges relating to the wreck.