Two Armed Response Vehicles (ARVs), a dog unit, two vans and two other Police cars silently responded to Nelson Street in the town at around 21:20 before descending on a first floor flat.
A battering ram, which is used to force entry to a property, was seen to have been used by officers.
An eye witnesses has told Island Echo how a similar raid was carried out on the same property around 4 weeks ago.
UPDATE THURSDAY: A spokesperson for Hampshire Constabulary has this morning confirmed that a man, aged in his 50s, has been arrested on suspicion of being concerned in the supply of heroin.
A female, aged in her 20s, was also arrested at the address in Nelson Street last night on suspicion of possessing heroin.