Officers received a tip-off about Alexander Cocktail Bar, on Shambles Street, which has been empty for about eight months.
A raid took place last month which resulted in officers uncovering hundreds of plants, thought to be one of the biggest hauls of cannabis officers in the town have ever had.
Sgt Matt Wood said: “It’s still an ongoing investigation and forensic evidence is being gathered, but this was a commercial-scale set-up so it’s a very good find.
“Often when we uncover cannabis plants they’re in the loft, but on this occasion the whole building was full.”
Alexander Cocktail Bar, which was formerly a Chinese restaurant called Red Ginger, was last run by 29-year-old Romanian Andrei Tuculianu, who is named on Companies House as a director.
The find comes just weeks after the Kendray-based policing team found more than 200 plants at a house in Wombwell, which had an estimated street value of £200,000.
Police told the Chronicle no arrests have been made in relation to either cannabis finds, but enquiries are continuing and a joint investigation has been launched by neighbourhood and tasking police teams in the town centre and Wombwell.
South Yorkshire Police have become increasingly focused on dealing with cannabis ‘farms’, setting up a serious and organised crime vulnerability unit.
That has a team of specialist officers working to identify people and to bring those involved to justice.
In future, they will be working in tandem with Barnsley Council and charities which work to help safeguard survivors and victims of the crimes under the newly-created South Yorkshire Modern Slavery Partnership.
Det Sgt Nikki Leach told a launch meeting for the partnership this week: “There is a rise in the numbers being forced to cultivate cannabis. The person involved in cultivating cannabis is probably not going to be Mr Big and is probably exploited.
“We have been trying to change the mindset of officers to look at the bigger picture and to treat that person as a victim.”