By Josh Ong

Published: 04:41 AM EST (01:41 AM PST)

Apple supplier and manufacturing partner Pegatron said 61 workers had been injured as a result of an explosion at a subsidiary's metal casing factory in Shanghai, China.

Pegatron Chief Financial Officer Charles Lin reported the incident, noting that the facility in question was still under construction, according to Reuters. 23 workers were hospitalized after the gas explosion, which occurred on Saturday at a metal casing factory belonging to Ri-Teng Computer Accessory Co.

"The factory has not started operations yet. Part of the facility is still under pre-operation inspection and part is running trial production," he said.

Apple responded that it was looking into the matter.

"Our hearts go out to the people who were hurt in Songjiang. We are working closely with Pegatron to understand the cause of this accident," said spokeswoman Carolyn Wu.

Taiwan-based DigiTimes reported that Ri-Teng was expanding the facility in order to compete with rivals Catcher Technology and Foxconn over metal notebook casing orders. Industry sources told the publication that Pegatron will spend $300-400 million procuring computer numerical control (CNC) machines next year in hopes of becoming one of the top-three suppliers.

Notebook makers are said to have been frustrated by the limited supply of CNC machines, as Apple has commandeered most of the available capacity for its unibody Macbook chassis. Vendors have especially been interested in utilizing metal chassis for Intel's new ultrabook standard, but reports suggest that many have been unsuccessful in acquiring the necessary capacity.

Catcher has experienced its own recent setbacks to its China-based metal chassis production operations. In October, local officials ordered a factory in Suzhou to temporarily close because of odorous gas emissions. The supplier's Suzhou factory reportedly supplies 60 percent of the unibody enclosures bound for Apple's MacBook Pro and MacBook Air portables.

Apple's supply chain in China has come under scrutiny as a result of several recent high-profile incidents. In May, three employees were killed and 16 injured at a Foxconn factory producing iPad 2 units in Chengdu, China when a dust explosion occurred at the facility's "polishing plant." Foxconn has also been criticized because of the growing number of employee suicides that have occurred on its property.

Chinese environmental protection groups have been meeting with Apple to discuss concerns that its suppliers are taking advantage of loopholes to get away with excessive pollution. The Cupertino, Calif., company subsequently agreed to ask each of its suppliers that have been identified as gross polluters to reform. Pegatron, in particular, has been called out by environmental groups as being a flagrant polluter.