Officers executed a search warrant at a property in London Road, North End, across the road from the junction with Mayfield Road, on Friday afternoon.
As The News has previously reported, a cordon was set up and firefighters put up a tent outside the building.
Firefighter Garth Waterman from Cosham Fire Station described it as a ‘sensitive’ incident.
A spokesman for Hampshire Constabulary said: ‘At 3.07pm, officers entered a flat in London Road, Portsmouth to execute a search warrant.
‘Upon entry, chemicals were discovered and enquiries are ongoing around this.
‘A 34-year-old man from Southampton, a 33-year-old man from Landport and a 30-year-old woman from Landport were arrested on suspicion of drug-related offences.’
The three men have since been released from custody but remain under investigation.
A message from the Editor, Mark Waldron
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