NINE people, including children, were treated in hospital after they came into contact with highly toxic mercury that had been dumped.
The alert was sounded by Cleveland Police on Monday after the discovery of a glass vessel containing about 2oz of the highly poisonous metal.
The nine, who were taken to the James Cook University Hospital, in Middlesbrough, were aged from six to their early 20s.
The container is believed to have been smashed and was found in a bin in Slater Road, Grangetown, near Middlesbrough.
Traces of the metal, which can cause severe breathing difficulties and other problems, were found in Stafford Road and The Broadway.
Acting Inspector Geoff Tate said one witness reported seeing people scooping up the mercury with their hands.
A clean-up operation was launched by the fire brigade at 10pm.
Anyone who believes they have been contaminated has been urged to seek immediate medical attention.
The nine who went to hospital for treatment were discharged. Experts said one small exposure was unlikely to cause long-term problems.
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