People have been seen wading into the water along the Sussex coastline to grab timber from a cargo ship which sank off the Dorset coast.
Coastguards said anyone who finds timber must report it
The Greek-registered Ice Prince went down about 26 miles (42km) off Portland Bill after being damaged in a storm.
She shed more than 2,000 tonnes of her 5,260-tonne timber cargo. An exclusion zone is in place around the ship.
The timber is reported to be coming ashore along the south coast between Selsey Bill and Brighton.
Colin Griffiths, Solent Coastguard watch manager, said: "The first report of people wading into the water at Selsey Bill in West Sussex came in at 0830 GMT.
"There have also been reports this morning of timber washing ashore at beaches in Littlehampton, Shoreham, Bognor Regis and Worthing.
"I believe the timber is likely to float as far as Newhaven and even Beachy Head.
"We are determined not to have a repeat of the Napoli."
When The MSC Napoli ran aground off the Devon Coast almost a year ago, scavengers swarmed to Branscombe in search of plunder.
Police and coastguards are now at some Sussex beaches trying to stop people taking the cargo, which will be removed by contractors, added Mr Griffiths.
Worthing beach has now been closed, said West Sussex County Council.
On Thursday, The Maritime and Coastguard Agency (MCA) warned people who keep the washed-up timber from the Ice Prince could be arrested and fined up to £2,500.
Under the Merchant Shipping Act 1995, it is an offence to conceal or keep possession of such cargo, or to fail to report the cargo.
The agency said the risk of oil pollution was low, but they were concerned the "wood slick" of the cargo could be a hazard to shipping.
Windsurfers in the region have been criticised for pursuing their sport among the huge timber planks coming ashore between Selsey Bill and Worthing.
"We think it is madness to go windsurfing among all this wood," said Maritime and Coastguard Agency spokesman Mark Clark, who said people were causing "quite a lot of problems".
"With all this wood coming in it does create problems and we do not want any casualties or accidents," he said.
The 10m (33ft) lengths of wood were put on board in bundles, but sea conditions broke many of them apart.
Representatives of the government, police, councils, the ship's owners and salvors have met to discuss how to minimise the impact of the cargo or leaked oil.
The 6,395-ton Ice Prince sent out her initial emergency call at about 1900 GMT on Sunday.
Rescuers battled gale force winds and rough seas with 16ft (5m) swells to remove the vessel's crew.
Twelve were airlifted to Portland, Dorset, and eight others taken by lifeboat to Brixham, Devon.
The 328ft (100m) ship finally sank at about 0045 GMT on Tuesday in 9ft (2.7m) waves and strong winds.
All timber sighted must be reported to Solent Coastguard by telephoning: 02392 559021 or 02392 559022.