DANBURY — An extensive investigation into a suspected drug conspiracy turned up several pounds of marijuana along with crack cocaine and led to three arrests last week, police said in a news release Wednesday. Members of the police department’s Special Investigations Division and Community Conditions Unit recently identified an apartment at the Linron Gardens condominium on Park Avenue as “the hub” of the suspects’ illegal drug sales. Hours before detectives planned to search the apartment, police arrested one of the suspects during a traffic stop on Backus Avenue.