Workers at a Foxconn factory in Shenzhen, China.
Hong Kong (CNN) -- The Chinese manufacturer of many of Apple's products has denied allegations that it forced students to work on its assembly lines in a last-minute push to ready the iPhone 5, expected to be unveiled Wednesday.
In a statement, Foxconn Technology Group denied it was forcing anyone to work and said the students -- who constitute 2.7% of its 1.2 million workers -- "are free to leave the internship program at any time."
"Foxconn has long had a short-term internship program that we carry out in cooperation with a number of vocational schools in China," the company said. The internship programs range in length from one to six months and students all are of legal age to work, the company added.
Foxconn's statement follows claims by a Chinese labor group that many of the students weren't given a choice by their schools whether to work on the assembly line.
"We think that this kind of internship is a sham and a kind of forced labor or involuntary work," said Debby Chan, a spokesperson for the Hong Kong-based Students & Scholars Against Corporate Misbehavior (SACOM). "The placement to work must be relevant to studies and the students must find it beneficial."
The group had interviewed students from a vocational school who were required to do internships at Foxconn's Zhengzhou plant even before the students started first year classes, Chan said.
The allegations follow a report last week by state-run China Daily that claimed vocational schools in Huai'an in Jiangsu province were making students work at a Foxconn plant making USB data lines for the new iPhone 5. Education, English, food science and finance majors were among those required to do paid assembly line internships. "I don't think we can improve our skills through that 'internship' the schools are requiring," one student told China Daily.
Apple has scheduled an event for Wednesday, anticipated to be the release of its latest iPhone.
Foxconn is part of Taiwan-based Hon Hai Precision Industry Co., one of the world's largest suppliers of components for the electronics industry. Much of its manufacturing division is based in mainland China, where it assembles a range of products including Apple's iPhone and iPad, Amazon's Kindle and Microsoft's Xbox.
"A recent audit of three of our facilities in China carried out by the Fair Labor Association confirmed that there was no evidence to indicate that any of the interns were pressured to participate in or to continue to participate in any internship program," Foxconn said in a statement. "A previous audit by the Fair Labor Association confirmed that students find their participation in this program valuable and that the positions offered by Foxconn were at compensation levels equivalent to entry-level full-time workers."
The Fair Labor Association released a report last month that Foxconn has moved to bring working hours -- including overtime -- down to below 60 hours per week "with the goal of reaching full compliance with the Chinese legal limit of 40 hours per week, plus an average of 9 hours of overtime per week while protecting worker compensation."
"Immediate health and safety measures" had been made, such as enforcement of breaks, changing equipment design to reduce repetitive stress injuries and testing of emergency equipment like eyewashes and sprinklers, the August report said.
Foxconn has been at the center of a storm of complaints about working conditions for its Chinese staff after a 2010 spate of worker suicides at its plants. Foxconn said it had increased workers pay, introduced counselors, started a 24-hour phone counseling service and opened a stress room where workers can take out frustration on mannequins with bats.
An explosion last year at a Foxconn plant that makes Apple's iPad2 in Chengdu killed four people and injured 18 more. Chinese officials said the blast may have been caused by combustible dust in a polishing workshop. That incident followed a report by SACOM alleging that workers at the same plant do not have adequate training in the use of chemicals and do not have regular on the job health checks.
"While we provide vocational schools with our qualification requirements, it is the schools that recruit the students under the supervision of the relevant local government and the schools also assign teachers to accompany and monitor the students throughout their internship program," Foxconn said on its use of interns.
"In addition to allowing the students to gain relevant industry experience while earning the same industry-competitive compensation as our full-time entry-level workers, this program gives Foxconn an opportunity to identify participants in the internship program who have the potential to be excellent full-time employees should they wish to join our company upon graduation from their vocational school."