Police used a battering ram to get into a Worthing flat early this afternoon.
After several swings officers managed to break the door open and crawled inside through a small hole.
Officers in riot gear and carrying shields entered the apartment in Newland Road about 12.10pm.
Once inside they conducted a search for evidence of drug-related crime.
Police remain at the scene processing evidence and enquiries are ongoing.
Pictures and video interviews to follow.