Harry Bell testified at an official inquiry into the November disaster that he’d told mine managers their plans to have a single entrance were “madness” and he feared the gas ventilation system was inadequate.

Bell, whose nephew was killed in the explosion, spoke Thursday as an expert witness. He criticized the lack of regular inspections at New Zealand mines following regulatory changes in the 1990s.

A three-member commission is probing the cause of last year’s methane-fueled explosions. The commission could recommend changes to New Zealand’s mining industry.