Heating and lighting equipment was installed in the houses

Police seized 1,500 plants from 10 houses in County Durham, Sunderland and Tyneside, where heating and lighting equipment had been installed.

Twelve men and a woman, mainly illegal immigrants, admitted conspiracy to produce cannabis.

Their drugs yield was valued at about �220,000, Teesside Crown Court heard.

The gang paid out thousands of pounds in advance to rent the houses in Lanchester, Bowburn, Sacriston, West Cornforth, Ushaw Moor, Bearpark, Sunderland and High Heaton.

In sentencing, Judge Peter Bowers said they had taken part in a large-scale, highly-commercial and organised drugs business, producing the powerful "skunk" strain of cannabis.