Supt Kevin Purcell, of West Mercia Police has said four children were playing near the lock, but two fell in and another then went to try and get them out, while the fourth ran home to raise the alarm.
This video shows the canal where three children entered the water. Police say they are 'working hard to establish exactly how Imie came to be in the water'.
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The high street chemist - which charges almost £15 more for the pill than rivals - said it was "truly sorry" for a "poor choice of words".
A 31-year-old man has been missing since yesterday morning.
A festival will take place this weekend to pay tribute to Christina Edkins, who was killed on a bus in 2013.