A woman in her 40s was pronounced dead by paramedics after they were called to an address near the town centre.
The alarm was raised after the woman was found collapsed in a flat in Stonegate Street, near the waterfront, on Saturday afternoon.
A spokesman for the East of England Ambulance Service said a quick response vehicle, ambulance and the air ambulance were sent to the scene.
Efforts were made to resuscitate the woman but she was pronounced dead at the scene.
Police were also in attendance. But the woman's death is not being treated as suspicious.
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