Two men have denied producing drugs at the biggest cannabis factory ever in Hertfordshire – which police uncovered in Letchworth last month.

The Comet: The largest ever cannabis factory in Hertfordshire, discovered in a Letchworth industrial unit. Picture: Herts policeThe largest ever cannabis factory in Hertfordshire, discovered in a Letchworth industrial unit. Picture: Herts police (Image: Archant)

Tuan Nguyen and 20-year-old Ba-van Nguyen were arrested after the factory was discovered in a Letchworth industrial unit, with what police said was a potential annual crop worth £1.5 million – making it the the biggest ever in the county, the force said.

The factory was found on the Woodside Industrial Park, off Works Road, after specialist officers from the Operation Support Group acted on intelligence from members of the public.

More than 1,300 plants were recovered from seven growing rooms that had been concealed behind false walls.

The two men, who are both of unknown abode, have denied the charge of producing cannabis and have been remanded in custody. They are next set to appear at St Albans Crown Court on May 18.

The Comet: The largest ever cannabis factory in Hertfordshire, discovered in a Letchworth industrial unit. Picture: Herts policeThe largest ever cannabis factory in Hertfordshire, discovered in a Letchworth industrial unit. Picture: Herts police (Image: Archant)

Tuan Nguyen had been recorded as 16 years old when arrested, but following a hearing at Luton Magistrates’ Court has been deemed to be over 18.