After the explosion traced to the polishing workshop at the Chengdu factory, Foxconn shut down its polishing workshops at other factories for a review of all safety policies and procedures at the workshops.

The investigation into the explosion at the facility in Chengdu is ongoing, Foxconn Technology Group said in a statement on Thursday. It did not give a date for the reopening of this facility which makes Apple's iPad 2.

Foxconn has another facility in Shenzhen that makes most of the iPads, but some analysts have raised doubts whether the factory at Shenzhen can make up for the disruption of production at Chengdu.

Research firm IHS iSuppli said in May that if production at the Chengdu factory is disrupted until the end of June, it could result in a production loss of about 500,000 units of the iPad 2 in the second quarter.

Foxconn said on Thursday that while the investigation into the Chengdu blast continues, it has addressed the preliminary finding that the accident was likely due to an explosion of aluminum dust in a ventilation duct. The company said it had put in place improvements in workshop ventilation, revamped its policies and practices relating to the disposal of the dust, and applied new technologies that will further enhance the safety in these workshops.