Unravelling the plot that left four men dead... was it an accident, or something more sinister? The mystery may never be solved

They died in terrible circumstances 6,000 miles away from their families in Vietnam, modern day slaves who appear to have been trafficked here by gangmasters to work on a huge cannabis farm in a converted mill under the noses of neighbouring businesses trading legitimately.

Exactly how the men met their deaths in a devastating fire at Bismark House Mill on Bower Street, Oldham on May 7 last year - whether it was an accident or something more sinister - remains a mystery that may never be solved.

That's because those who brought them here and profited from their toils were involved in two forms of very serious crime: modern slavery and the cultivation and supply of illegal drugs.

What we do know is that somehow their bodies weren't discovered until two months after the fire, when demolition workers found human remains, prompting headlines all over the world.

As the net closes on the gangmasters, M.E.N. crime reporter John Scheerhout has been granted rare access to the continuing police investigation into the fatal fire, and has interviewed the detective tasked with bringing justice to families desperate for answers on the other side of the world.

Behind each name is a devastated family in rural Vietnam: Uoc Van Nguyen, 31, Cuong Van Chu, 39, Duong Van Nguyen, 29, and 21-year-old Nam Thanh Lee.

Precisely how these young men got to the UK - whether in boats across the Channel or in the back of lorries - hasn't yet been established. But they were all here illegally and one of them, married father Cuong Van Chu, is known to have arrived here in June, 2019, suggesting the cannabis farm had been functioning for at least two years before it was destroyed by fire.

That, potentially, means the farm was a multimillion