The gangsters struck on Friday night and made away with 48 bags of the commodity belonging to the farmers.
According to the farmers, four night guards were on duty when the gangsters raided the factory.
They attacked the guards and tied them with ropes before they forced their way into the stores, loaded coffee beans into sacks, which they loaded into a lorry and drove off.
This is the fourth factory to be raided by a well-organised gang in the region in the past one month..
The guards were rescued on Saturday morning by residents who responded when they heard screams for help.
The farmers said coffee theft in the region had become rampant and told the police to get to the bottom of the matter.
They said the gangsters had dealt a big blow to them and called on police to pursue the thieves and recover the the stolen coffee.
County police commander Joseph Nthenge said they suspected the theft was an inside job.
However, he said investigations had been launched with a view of identifying those who took away the coffee.
Mr Nthenge criticised officials of various coffee societies of ignoring his advice to seek police security.
“We held a meeting with the officials recently and I advised them to ask for police security when they have coffee in stores. I told them that we can guard the coffee until it is delivered to the market but they have not taken my advice seriously,” he said.
Mr Nthenge said some officials of the factory would be investigated.
“We may start investigating some of these officials and possibly have them prosecuted,” said Mr Nthenge.