Earlier this month, the force said 24 people had been charged with possession with intent to supply Class A drugs.
On Friday, it said five more people had now been charged, bringing the total to 29 and they are all from the city.
Police raided 35 addresses on 26 April during an operation involving 200 officers.

Walt Disney said subscriber numbers for its sports channel ESPN had dropped. Viewers are moving away from packages offered by cable companies to simpler services and stand-alone streaming.
Time Warner also fell 9%, despite better-than-expected profit  figures.
The Dow Jones shed 0.06% to 17,067 points.
The S&P 500 gained 0.31% to 2,099.88 points. The Nasdaq rose 0.67% to 5,139.95 points.
Discovery Communications fell 13% after reporting lower advertising sales and a strong dollar for below forecast profits.
Twenty-First Century Fox were down 7%, CBS down 5% and Viacom shares 7%.
Barton Crockett, an analyst at FBR Capital Markets, said: "If Disney can get dinged, maybe nobody's safe."
But bucking the trend, Dish Network reported higher-than-expected revenue and profit and shares rose 4%.
Priceline Group rose 6% after the travel company reported profit and revenue that beat analysts' forecasts.
First Solar, up 17% and Ralph Lauren, turned an earlier 2.3%, gain into a loss of 1% despite releasing results that pleased investors.
Economic data was disappointing.
Private employers hired 185,000 workers last month, according to the ADP National Employment Report. That fell short of economists' forecasts for an increase of 215,000.
The report also revised down June's private payroll gains to 229,000 from the 237,000 reported before.
Investors will be looking to Friday's non-farm payroll data.
Twenty-nine people have been charged following drugs raids in Newport, Gwent Police has said.
[NEXT_CONCEPT]
(Close): Disney shares closed down 9% after disappointing earnings figures sparking share price falls in rival cable companies.