Corrosion in a single pipe was behind an explosion and fire at the Co-op refinery in Regina last fall, fire inspectors said Thursday.
Their report said a tear almost 18 centimetres long triggered the initial explosion and subsequent smaller ones.
The problem was in a diesel fuel processing area and had got worse since 2008 when practices at the plant changed, the inspectors said.
Co-op officials said tests had not shown any problems with the pipe.
"In short, something was missed," Co-op CEO Scott Banda said after the report was released.
Seven contract employees who were working on a $2-billion upgrade and expansion were taken to hospital and two more were treated at the plant for burns.
Another 1,400 people had to leave the refinery after the blast triggered a huge fireball that could be seen all over the city.
Banda said some corrosion was detected in 2010, but he said all of that pipe was replaced before the blast. Protocols were followed, he said, noting that 94,000 spots are checked on a routing basis.
"Now is that enough, is that too many? I don't know, but clearly they didn't work," he said.
