A man was led away in handcuffs as police shut down two drug dens above an Age Concern charity shop.
Police and Police Community Support Officers found rooms at the two flats on separate floors in London Road, Brighton, littered with hypodermic needles and other drugs paraphernalia.
The flats were closed for three months on Wednesday under the Antisocial Behaviour Act 2003, which is designed to tackle the unauthorised use of premises for drugs.
Inspector Nev Kemp, of Sussex Police, said: "Used needles were all over the place, on floors, under a bed and even in a bread bin.
"It was very dangerous for the officers."
Mr Kemp said the man arrested, in his 20s, was suspected of possessing heroin and was in breach of previous closure notices.
They were first issued on both premises on May 16 in connection with disorder associated with drug dealing.
The notices allowed only the occupiers of the premises to be there at any time.
Brighton magistrates granted the three-month closure orders this week after hearing two hours of evidence about drug use and antisocial behaviour.
Mr Kemp said as workmen were boarding up the premises, passers-by stopped and congratulated police.
He said: "They were fed up with all the bad behaviour, comings and goings all day and night and obvious drug use going on."
A female volunteer at the Age Concern shop said: "We're delighted. It's been mayhem up there with unruly behaviour and huge amounts of noise.
"We are delighted it is over. It has been very scary. We're thrilled."
Heavy-duty steel covers were placed over the doors and windows to prevent the properties being entered.
The rooms are owned by a housing association which, ultimately, will refurbish the premises and let them to vetted tenants.
Chief Inspector Steve Barry, of Sussex Police, said: "These premises have had a negative impact on community life as a whole and I'm sure now that they are closed, local people will see a difference to their quality of life.
"We are committed to using these powers to work with partner agencies in tackling drug dealing in the city and we will continue to tackle these problems head on and target problem properties so people do not have to live in fear."
Anyone with information about drug dealing should contact Sussex Police on 0845 6070999.
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