Twenty current and former employees at an Amazon warehouse in Pennsylvania say they were forced to work in brutal heat at a breakneck pace while hired paramedics waited outside in case anyone became dangerously dehydrated.

Spencer Soper has published an exhaustive investigation into the massive online retailer's Lehigh Valley, Pennsylvania operation. Soper reports that a local doctor treated employees at the facility for heat-related health problems, and wound up filing a complaint about conditions there with federal regulators. Many of the warehouse's employees were temporary and hired through a staffing company; if they did not meet packing quotas, they faced daily threats of termination, Soper writes.

He also notes that a corps of other temporary workers were poised to replace any freshly fired Amazon employee. "The safety and welfare of our employees is our No. 1 priority at Amazon, and as the general manager, I take that responsibility seriously," Amazon warehouse manager Vickie Mortimer told the paper.