ISLAMABAD, Pakistan — A prominent factory monitoring group heavily financed by industry gave a clean bill of health to a Pakistani apparel plant last month, just weeks before a fire engulfed the premises and killed nearly 300 workers, many of them trapped behind locked exit doors.

In August, two inspectors who visited the factory, Ali Enterprises in Karachi, to examine working conditions gave it a prestigious SA8000 certification, meaning it had met international standards in nine areas, including health and safety, child labor and minimum wages. The two inspectors were working on behalf of Social Accountability International, a nonprofit monitoring group based in New York that obtains much of its financing from corporations and relies on 21 affiliates around the world to do most of its inspections.

Weeks later, a fire swept the plant on Sept. 12, trapping hundreds of workers in a building with barred windows and just one open exit, resulting in one of the worst industrial disasters in history — one that killed nearly twice as many workers as the landmark Triangle shirtwaist factory fire of 1911 in New York.

The Karachi tragedy is a huge embarrassment to the factory monitoring system, in which many Western garment and electronics companies rely on auditing groups to provide a coveted seal of approval to their low-cost suppliers in the developing world.