Police in Northumberland are warning about a legal high circulating in the Ashington area.
A 16-year-old boy who had taken a substance called Salvia has been arrested on suspicion of assaulting a baby, and a pupil from Ashington High School was taken to hospital after collapsing.
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Laura Pidcock was among those to raise the issue at Prime Minister's Questions.
Mark Shaw was bound, beaten, bitten, gagged, attacked with weapons and stabbed to death in Grange Villa, County Durham, last December.
But Theresa May has refused Labour's call to halt the roll-out of Universal Credit, insisting the new benefits system was "working".