Food delivery giants Ele.me and Meituan-Dianping have asked restaurants using their platforms to examine their suppliers and report any adulterated or contaminated food to the food and drug authorities.

The statements, published on the companies' social media accounts on Friday, followed the posting of a video on social media that showed unhygienic conditions and substandard food in a factory making seasoning packets and packaged meat in Anhui province.

Ele.me and Meituan-Dianping said they have removed restaurants that have used ingredients produced by the GangGang-Xiang food factory in Hefei, Anhui, from their online delivery platforms and halted delivery services.

The factory found itself in hot water after footage of dirty floors, unsanitary handling of food and year-old expired meat was posted online on Friday. The video showed expired meat being processed, packaged and sent to restaurants.

The video, which also showed staff members cooking expired and unclean meat without wearing gloves, said Gang-GangXiang sells around 40,000 packages of meat a day across eastern China.

"The meat was there for almost a year. We bought tons of it just because it was cheap," one restaurant employee told ThePaper.cn. "The food is disgusting, and we do not want to eat it ourselves."

The two food delivery giants took action after it was revealed that the factory had been supplying restaurants operating on their platforms.

Meituan, which had 290 million monthly active users as of April, and Ele.me, with its 50 million users, have ordered food businesses to inspect their purchasing channels, ensure the quality of ingredients that go into their dishes and remove all items that could cause a public health hazard.

China's food delivery market grew rapidly last year, with young Chinese increasingly choosing to order food online, a report showed.

The online food delivery market hit 204.6 billion yuan ($32.5 billion) last year, 23 percent more than the previous year, according to a report by Meituan.

In May, Ele.me and Meituan launched separate investigations into illegal or otherwise unqualified vendors as part of a wider crackdown on food safety violations in Beijing. As of May 12, Ele.me had delisted 7,926 Beijing takeout restaurants and Meituan had removed 7,247.

Similar efforts were made in Shanghai two years ago, when city officials announced new regulations requiring delivery service providers to ensure that their partner restaurants were properly licensed.