The Norwegian Environmental Directorate has removed some 'slime' toy products from the market after it found they contained illegal levels of the reprotoxin boron.
Of 14 products tested from online and high street stores, six leached over three times the permitted limit, the directorate said.
Boron compounds, such as borax, are added to toy slime to give it a gelatinous texture.
Some products also had high levels of the preservatives MI (2-methyl-2H-isothiazol-3-one) and CMI (5-chloro-2-methyl-2H-isothiazol-3-one). Used to prevent fungi and bacteria, they face EU regulatory controls for water-based materials in toys.
Slime products are often imported into Norway, the Directorate said, adding it has stopped several containers of slime and putty that were not CE marked or lacked the necessary test reports to show compliance.
It urged retailers and importers to ensure routine checks on safety of products they sell are in place, and to request test reports from the manufacturers, Mathieu Veulemans, the directorate's product supervision director, said.
In April, the directorate removed other ‘slime’ toys from the market after it found they contained high levels of lead and arsenic.
EU countries have also been warning about harmful chemicals contained in slime used in toys. In July, UK consumer group Which? said slime toys can contain boron compounds exceeding EU safety limits, and similar warnings have been issued in Finland and France.