The labour protection department of the district in Shanghai where Pinduodouo is headquartered is looking into the company's working hours and employment contracts, according to a report in the Beijing Youth Daily on Monday.

Changning district's labour protection department did not respond to Reuters' calls for comment. Pinduoduo declined to comment.

The company confirmed that a female employee collapsed while walking home from work with a colleague in the early hours of December 29. She later died in hospital, the company said in a statement.

The cause of her death was not disclosed. Pinduoduo declined to comment on its work policies.

The death has reignited criticism of the long hours commonly practiced in China's tech industry, where a so-called "996" culture, which refers to employees working from 9 a.m. to 9 p.m., six days a week, persists despite pushback from workers.

The topic "Pinduoduo employee" was among the top 20 subjects trending on China's Twitter-like Weibo, receiving 224 million views and 23,400 comments.

Shares of Pinduoduo, China's third-largest ecommerce platform after Alibaba and JD.com, are listed on the Nasdaq in New York.

(Reporting by Sophie Yu and Brenda Goh; Additional Reporting by Shanghai Newsroom; Editing by Carmel Crimmins)