As Apple shares zoomed up and breached the $500 mark on Monday, company officials revealed at the same time that independent inspectors from the Fair Labor Association (FLA) have begun their probe on Apple assembly facilities in China.

In a statement, Apple said that inspectors from the labour advocacy group arrived Monday morning in Shenzhen, China for scheduled trips on the Foxconn assembly compound where tech gadgets from Apple, Microsoft and other tech firms were being manufactured by more than one million Chinese workers.

The huge numbers of employees were under the care of the Hon Hai Precision Industry, the Taiwanese manufacturing partner of Apple responsible for putting together the bestselling iPhones and iPads.

Labour advocates, however, also accused Hon Hai of running virtual sweat shops in China that employ under-paid and underage workers who were made to work long hours especially during release periods of Apple products.

Labour negligence and abuses occurring in Foxconn facilities have been blamed by media reports and activists as responsible for the number of deaths that visited the Apple assembly plant in 2010.

Workers have reportedly committed suicide within the Foxconn premises while accidents claimed the lives of at least three workers over the past two years, according to the Associated Press (AP).

Despite the numerous accounts of deaths and abuses happening on Foxconn facilities, labour advocates scored Apple officials for turning a blind eye on the appalling condition of its overseas workers, partly responsible for its continued success.

Just this week, Apple reached a total market capitalization of $465 billion, making it as the planet's most valuable company.

Apple, however, claimed that it was making headways on efforts to improve the lot of workers commissioned to assemble the gadgets that defined the tech habits of hundreds of millions around the world.

Apart from its internal audits, which Apple said resulted to working condition improvements for its workers, the American tech titan joined the FLA in January, in hopes of lending credence to its claims of overhauling the Apple supply chain system.

The FLA inspections are expected to last until early March and will cover some 90 percent of manufacturing installations where Apple products were being assembled, Apple said.

The company added that results and recommendations coming out of the FLA inspection will be posted on the labour group's site, www.fairlabor.org.