Foxconn Electronics, a Taiwan-funded supplier of Apple, has denied that benzene exposure led to several leukemia cases among employees at its plant in South China's Shenzhen city.

In a written reply to Xinhua, the company said employees who suffered leukemia had different jobs and they had no direct contact with benzene in their work, citing a preliminary investigation.

Earlier this week, British newspaper The Daily Mail reported that at least 13 Foxconn workers in Shenzhen had been diagnosed with leukemia and five died.

According to Xinhua investigations, nine employees in Foxconn's Shenzhen factories have been diagnosed with the disease since 2010. Seven of them were confirmed with leukemia between August 2010 and December 2011, and five of them have died, .

One employee surnamed Yi, 24, is being treated in Shenzhen No.2 People's Hospital for leukemia. He started work in Foxconn in March 2010 and was diagnosed with leukemia in December 2011.

He first worked in a department for cleaning aluminous materials for about one month and was then transferred to other departments, according to his mother.

"No one in our family has ever had cancer before. When we heard the news, I could not accept the fact," she said.

Yi's contract with Foxconn expired in October 2013. Foxconn offered Yi a compensation of 39,000 yuan, or about his salary for one year and ended his contract.

Another employee surnamed Feng began to work in the plant in February 2011 and was diagnosed with leukemia four months later. He died in November 2013.

Feng's work was encasement and distribution of materials. The family owes 400,000 yuan because of Feng's medical treatment, according to his parents. Feng received nearly 90,000 yuan from Foxconn during his hospitalization.

During his treatment, Feng suspected his disease was related to his work and attempted to speak to executives, but was refused, said the parents.

A written response to a petition in 2012 from the Shenzhen Health and Family Planning Commission showed the seven employees had no direct contact with benzene. Possible toxic materials they were in contact with included lead and sulfuric acid.

On-the-spot investigations by professionals are needed to decide whether the leukemia is job-related, said Zhuo Jiacai, a doctor of Shenzhen No.2 People's Hospital.

It is difficult to confirm the relation between sickness and working environment, said Wei Qian, a researcher on labor law at Peking University.

Patients have difficulties in providing evidence if they turn to lawsuits, Wei said, adding Foxconn should bear social responsibility and provide more care and aid to sick employees.