Police say they are extremely concerned after receiving a report a child may have been given drugs in her trick-or-treat bucket.
Tests are being carried out on unknown pink tablets that were handed over to a girl in Shiremoor, North Tyneside, on Halloween night.
Her mother contacted police with concerns about what had been placed in the bucket and an investigation was launched
The force said it takes such reports seriously.
A Northumbria Police spokesperson said: "We are investigating a report from a parent that unknown pink tablets were placed in her daughter's trick or treat bucket in Shiremoor last night.
"Enquiries to establish if the tablets are harmful are ongoing but any reports of this nature are extremely concerning and will be taken seriously by police."
Anyone else who has been given a similar tablet, or has information about what happened, is asked to call 101.