SHANGHAI (Bloomberg) - China Unicom Hong Kong executive director Zhang Junan is being questioned as part of an investigation of former chairman Chang Xiaobing, people familiar with the situation said.

The authorities are also probing Mr Zhang, though that does not mean he has necessarily committed any wrongdoing, said the people, who asked not to be identified as the matter has not been publicly announced.

Mr Ivan Wong, a spokesman for China Unicom, said by e-mail that Mr Zhang was cooperating with authorities in the investigation of Mr Chang. Mr Zhang has not been placed under "shuanggui", Mr Wong said, referring to a form of detention used in probes by the Communist Party that's outside China's legal system.

Mr Chang, who left Unicom to become chairman of China Telecom Corp., was being probed for severe disciplinary violations, the Communist Party's disciplinary watchdog said in December.

Mr Chang resigned from China Telecom after the probe announcement, the company said.