Apple has said that auditors from a labor rights group have begun inspections of the Chinese factories, including Foxconn factories in Shenzhen and Chengdu, which manufacture its iPad and iPhone.

Apple joined the Fair Labor Association (FLA) last month after acknowledging that aluminum dust was responsible for explosions at two of its Chinese suppliers last year that resulted in four deaths and injuries to another 77 workers. One of the two explosions occurred at a Foxconn plant in Chengdu, China, in last May. The other took place at a Shanghai factory run by RiTeng Computer Accessory, a subsidiary of Pegatron, another Apple supplier, two months ago.

“We believe that workers everywhere have the right to a safe and fair work environment, which is why we’ve asked the FLA to independently assess the performance of our largest suppliers,” Apple CEO Tim Cook said in a statement. “The inspections now under way are unprecedented in the electronics industry, both in scale and scope, and we appreciate the FLA agreeing to take the unusual step of identifying the factories in their reports,” he added.

According to Apple, the FLA team will interview thousands of workers, inspect manufacturing facilities and workers' living quarters, and review suppliers' documentation. The FLA findings and recommendations from the assessments will be posted on the FLA Web site in early March, according to Apple. The company added that its suppliers have pledged their full cooperation with the FLA. Investigations will also target other major suppliers, including Pegatron and Quanta.

In January, Apple released a list of 156 companies that represent 97 percent of procurement costs, along with its annual report on factories where the iPhone, iPad and other products are made.