Jake Levene, 21, from Tingley, Mandy Christopher Lowther, 20, and Lee Childs, 44, both from Morley, were arrested in April and have been charged with conspiracy to supply and conspiracy to export class A drugs.
They have been bailed until June 14 when they will appear at Leeds Crown Court.
Police said that forensic examinations confirmed that a synthetic opiod, Fentanyl, which is up to 100 times stronger than street heroin, and its analogue, Carfentanyl – which is 100 times stronger again -were present in a factory.
Greg McKenna, regional head of investigations at the National Crime Agency, said: “Working in partnership with our law enforcement colleagues, we have responded to a UK-wide threat which has resulted in three people being charged with conspiracy to supply and exportation of class A drugs.
“Our investigation is still on-going and we will continue to share information and intelligence to protect the public”
A 33 year-old woman, a 26 year-old man from Liversedge and a 21-year old male from Ardsley who were arrested at the time as those charged have been released pending further enquiries.
Fentanyl is prescribed for severe pain relief. Carfentanyl has no medical uses for humans. Both are Class A substances under the Drugs Misuse Act.