Police went looking for metal thieves in the Black Country – and came across one of the biggest cannabis hauls ever found instead.

More than 2,000 plants were discovered in a Willenhall factory while officers combed the area for stolen copper and lead. It is the largest find in recent years in the area and could be worth up to £2 million on the street. Officers were on the industrial estate in Wood Street near the Yale buildings on a two-day operation for metal theft task group Operation Steel.

But an alert officer smelt the pungent aroma of the plants emanating from one of the units and went to investigate.

Acting Sgt Vince Cope, from Darlaston Police Station, said: “We went back to get a warrant and gained access to the premises and we were stunned to find what was inside.”

The rented unit, which measured 20ft by 80ft, was packed full of cannabis plants being grown under heat lamps hanging from the ceiling.

Three men were arrested at the scene and are helping police with their enquiries.

Sgt Cope added: “This was no bedroom operation, it was a major commercial enterprise and this will make a major dent in the production and supply of cannabis in the area.

“It was a motherload of cannabis and although we had been looking for metal on this day everyone was very pleased with the result.”

The unit in Wood Street at the junction with Church Street had no name on the front of it and did not seem to have any fake front for what was hidden behind the doors.

A string of cannabis factories have been shut down by police over recent weeks in Walsall.

Just last week a cannabis factory was discovered at a house in York Avenue in the Alumwell area where more than 250 cannabis plants were seized and a 15-year-old boy was arrested on suspicion of cultivating cannabis.

He is now helping police with their enquiries.

Big cannabis hauls last month included around 1,000 plants found in a former sandwich shop.