Pharmaceutical giant AstraZeneca said Thursday that the head of its China operations had been detained, after reports the firm was under investigation for potentially illegal data collection and drug imports.

AstraZeneca shares fell 8% in London Tuesday, the biggest drop in four years following a fresh report that a Chinese investigation of the company has widened. AstraZeneca said last week that its China chief,

AstraZeneca said on Wednesday its China president Leon Wang had been detained by Chinese authorities and, although it did not know the reason, it did not believe it was linked to a large health insurance fraud case involving the company.