Police have also arrested a man, 43, in connection with the find
A security guard arrested near the London 2012 Olympics stadium on suspicion of possessing explosives has been released on police bail.
The woman, a 40-year-old dog handler, was detained on Tuesday evening after her vehicle was searched in a car park off Pudding Mill Lane, Stratford.
She was questioned at an east London police station and has been bailed to return next month.
A 43-year-old man from Wales has also been arrested in connection with the explosive find and remains in police custody.
Scotland Yard said the arrests were part of an ongoing investigation and are not terrorist-related.
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