State Highway 25 is closed to traffic from a point around 10 kilometres north-east of Waihi - on the road to Whiritoa and Whangamata.
Local Focus has been told the cause is a major slip which brought down a tree north of here.
Whangamata township is reportedly out of petrol. Thames-Coromandel Council is urging people not to drive.
A spokesperson says even roads that are open are likely to have debris which is yet to be cleared by firefighters.
State Highway 25 has also been closed on the other side of the peninsula south of Thames.
And there are major delays on State Highway 2 through the Karangahake Gorge.
Civil Defence centres have been set up in Papanui and Whangamata.
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