An explosion at one of two factories that make Apple’s new iPad 2 highlights the risks of a global manufacturing strategy that has cut costs but concentrates production in a few locations.

Foxconn Technology Group, the contractor that manufactures Apple’s iPhones and iPads, said the May 20 blast in the western city of Chengdu killed three employees and injured 15. The Taiwanese company said the blast was caused by combustible dust in a workshop that polished products. It said operations in workshops that do similar work at its other factories in China would be suspended pending an investigation.