Detectives who smashed a drugs ring operating across five addresses in villages close to Corby and Kettering discovered around 4,000 plants in the plush rented homes.

Yesterday, prosecutors at the first court hearing of five Chinese immigrants arrested during Wednesday's raids, placed the value of the drugs at half-a-million pounds – five times the initial estimated figure.

In March, a similar-sized operation at a drugs factory in George's Street, Northampton, was discovered although Northamptonshire Police have not yet placed a value on the three to four thousand plants seized there.

The five men accused of growing the cannabis that sparked this week's operation appeared before magistrates in Corby yesterday to answer charges of growing plants of genus cannabis for cultivation.

Co-accused Zi Ming Chow, 49, Ming Ming Shaun, 38, Ming Qi Chen, 22, Xin He Lin, 39, and Qing Lin, 27, were dealt with at two separate 20-minute hearings at the Elizabeth Street court.

The men, three of whom gave their professions as casual kitchen workers, were arrested during the operation at luxury homes at St Mary's Road in Kettering, East Carlton Park in East Carlton, Fox Street in Rothwell, The Hill in Middleton and Manor Court in Cottingham.

A Mandarin interpreter spoke on behalf of the men as none can speak English.

None of the men were able to provide fixed UK addresses, nor did any enter a plea to the charges against them.

Magistrates refused bail applications for Chen, Lin and Lin and all the accused were remanded in custody and ordered appear at the same court next Friday when magistrates are expected to send the case to crown court.

The homes involved in this week's raids remain cordoned off.