Extensive debris has washed up on islands off the Dutch north coast after some 270 containers including chemicals fell off a cargo ship in a storm.
As the extent of pollution became clear on five islands including Terschelling, coastguards searched the North Sea for missing containers.
The cargo fell off the MSC Zoe near the German island of Borkum, but the tide carried many of them to the south-west.
Initial images showed children's toys and TVs on Dutch beaches.
But officials said three containers carried toxic substances, and Dutch and German coastguards warned local people to steer clear of them.
One of those containers had a cargo of peroxide powder, and a 25kg bag of the chemical was found on the island of Schiermonnikoog on Thursday, along with several containers and their contents.
What happened to the MSC Zoe?
The Panama-registered ship is described as the biggest in Europe, with a potential cargo of 19,000 containers.
As Storm Zeetje buffeted northern Germany with gale force winds late on Tuesday night, 270 containers of Zoe's cargo fell off the ship as it made its way through the Wadden Sea from the Belgian port of Antwerp.
Waves of up to 10m (33ft) in height were reported on the night and images from the Dutch coastguard showed dozens of containers balanced precariously like dominoes on the deck, about to fall into the sea.
By Wednesday morning, strong tides had already swept some of the containers on to beaches on Terschelling, Vlieland and Ameland and Dutch and German coastguard planes scoured the sea for the others.
There were fears that other shipping could be damaged by the cargo. The Geneva-based MSC company which owns the ship has asked a salvage company to use sonar equipment to help retrieve the missing containers.
Overnight into Thursday, the MSC Zoe docked at Bremerhaven. Several containers were spotted in German waters and a further 11 were seen by the Dutch coastguard floating between the islands of Ameland and Schiermonnikoog.
How bad is the pollution?
By Thursday five Dutch islands in the Wadden Sea had seen debris from the MSC Zoe wash up on its beaches.
On Texel, Vlieland, Terschelling, Ameland and Schiermonnikoog volunteers were helping on Thursday to clear up the mess spilt the previous day. Around 100 soldiers were being sent to the islands part of the clean-up operation.
Among the rubbish found on Terschelling's long, sandy beaches were shoes, bags, cushions, chairs, TVs and plastic cups.
Children found pink toys among the rubbish.
Volunteers had to scoop polystyrene packaging from the dunes.
On Ameland, local officials said 130,000kg of debris had been cleared up along an 8km (five-mile) stretch of beach.
Further to the east, on Schiermonnikoog, a trail of plastic rubbish, shoes and light bulbs was found on the beaches. "This is truly a disaster. How are we going to clean this up?" said local environmentalist Cynthia Borras. "We were prepared for an oil disaster but not this."
Terschelling mayor Bert Wassink feared the clean-up could take a long time.
"We've never seen this before. It's becoming more common to see containers falling in the water but never before on this scale," he told public broadcaster NOS.
It was not all bad news on Terschelling. The latest exhibit on display in the local shipwreck museum in the town of Formerum featured an "army" of plastic ponies.
When the MSC Napoli ran aground off the south-west coast of England in 2007, 80 containers washed ashore. Police had to shut a local beach as people scoured the debris for motorbikes and other merchandise.
Police had to use old laws on scavenging that require people to return goods from the stricken ship.
Although some flat screen TVs were found in the debris on Wednesday, most concerns on the Dutch islands focused on the environmental damage to the area.