A cordon is in place in Bath as emergency services deal with an incident.
Avon and Somerset Police said they were called to reports of a woman approaching people with a bag in Stall Street at around 14:30 BST, which led to some people feeling unwell.
The force said it was not aware of anyone else falling ill but "as a precaution, emergency personnel are wearing protective clothing".
A police spokesperson said officers were working with ambulance and fire crews and have "well rehearsed plans for responding to such incidents".
They explained police were called by the ambulance service just after 15:00 BST.
An update is expected later.