Children have been spotted entering and leaving the Foxconn factory in China where Apple iPhones are made.

Renowned US performer Mike Daisey travelled to China, where he spotted children aged around 12 and 14 entering the Foxconn factory, which is Apple's biggest supplier.

In the audio report, Mike Daisey says he spoke with workers at the gates of Foxconn, including one very young looking woman.

In the report recorded for This American Life, Daisey says: "How old are you? And she says, I'm 13. And I say, 13? That's young. Is it hard to get work at Foxconn when you're-- and she says oh no. And her friends all agree, they don't really check ages. The outside companies do have inspections, but workers told me Foxconn always knows when there's going to be an inspection. So what they do then, they don't even check ages then. They just pull everyone from the affected line, and then they put the oldest workers they have on that line."

In Daisey's report, which you can hear in its entirety below, he says that the young woman said she was employed to wipe iPhone screens.

Brian Reed, the co-producer of the episode told Huffington Post via email: "I had been talking to Apple for several weeks about our show, asking them to come on the air and respond to Mike's story, and they never mentioned that either of these things were in the works. But they're a very secretive company, so who knows what was going on."

Following the show, which aired on January 6 2012, Apple announced that the Fair Labour association will for the first time be auditing all their suppliers.

When contacted by The Huffington Post, Apple pointed out that for the first time the company also released a full list of the 97 suppliers it works with worldwide.

Apple have been releasing a Supplier Responsibility Report (SRR) since 2007, and the 2011 report (released on Friday 13 January) reads: "We have a zero-tolerance policy for underage labor, and we believe our system is the toughest in the electronics industry. In 2011, we broadened our age verification program and saw dramatic improvements in hiring practices by our suppliers. Cases of underage labor were down significantly, and our audits found no underage workers at our final assembly suppliers."

Apple also emailed Huffington Post to reiterate that the company conducted 229 audits of its supply chain in 2011 - an 80 percent increase over 2010 - including more than 100 first-time audits. Apple also said that their training programs have also educated more than one million supply chain employees about local laws, and that more than 60,000 workers have enrolled in classes to study business and entrepreneurship, improve their computer skills, or learn English.

The Foxconn factory where Daisey conducted his interviews has been specifically targeted by Apple for improvements in worker welfare.

The 2011 SRR report says that in 2010, Apple worked with Foxconn to launch an employee assistance program (EAP) at the Shenzhen factory, giving workers free access to psychological counseling, including a 24-hour hotline.

The Foxconn factory has recently been at the centre of a mass suicide threat by workers. Approximately 150 Chinese workers at the factory where Apple iPhones and Microsoft XBox consoles are manufactured, stood on a roof and threatened bosses with suicide over a dispute about pay.

The International Labour Organization's conventions on child labour suggest that Foxconn may be acting appropriately by employing 13 year olds. Its guidelines read "Children between the ages of 13 and 15 years old may do light work, as long as it does not threaten their health and safety, or hinder their education or vocational orientation and training."

The ILO says that 200m children worldwide are still in child labour, while their 2012 report showed that number continues to decline modestly.

In February 2011, Apple said that 91 children were found to be working in some of its Chinese factories, according to The Telegraph.

Read Brian Reed's blog for more on the response to the report from Apple.

This is an amended version of a previous article.