Several AstraZeneca staff are under investigation in China for allegedly breaking the law.

The UK pharma giant said five current and former workers were being questioned.

Bloomberg reported that police were investigating the collection of patient data and importing unlicensed drugs, including a cancer treatment.

Astra said: 'We are aware a small number of our employees in China are under investigation and we have no further information to share at this point.'

The company has been operating in China since 1993 and made around £4.5billion in the country last year, 13 per cent of total sales. There is currently a crackdown on drug smuggling by Beijing.

But the investigation is blow for the FTSE 100 group, which has otherwise enjoyed huge success in recent months.

Shares are up nearly a fifth this year on the back of its blockbuster cancer drug, Imfinzi, and a pipeline of new pills.

Last month it was the first UK firm to be valued at more than £200bn, with Shell at £161billion. Just two others top £100billion: Unilever (£124billion) and HSBC (£121billion).