Lancashire River Wyre has a notorious reputation having claimed the life of a two-year-old boy, seen the body of a teenager wash up in it and been the scene of a deadly water plant explosion in 1984.
The woman in a red coat walking a white dog on a lead in St Michael s on Wyre north of Preston is being sought as a potential witness rather than a suspect in any crime.
The mother-of-two first started walking along the path lining the River Wyre, in Lancashire, at 8.43am, having already dropped her daughters, aged six and nine, off at school.