Police were called to a location on Nottingham Road, in Mansfield, after the discovery of a body at a former garage in the area.
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He demanded the money after placing a carrier bag containing what appeared to be a heavy object on the counter.
Closures will be in place on the Aston Expressway, Park Circus and Salford Circus. There will be some full weekend closures and diversions.
West Midlands Police have said specially trained police negotiators are speaking with the woman to try and talk her down to safety.