Food and drug officials in China announced on Friday that they have placed 35 restaurants, including a well-known hotpot chain in Beijing, under investigation after allegedly adding opium poppies to their food.

The China Food and Drug Administration (CFDA) said the establishments in question sprinkled their menu ranging from hotpot, noodles, hotpot, fried chicken and grilled fish with ground poppy powder, which contains low levels of addictive substances such as morphine and codeine.

Adding poppy powder to dishes is said to be a common among cooks in China, though it is unclear whether the practice can make food addictive to eaters.

Authorities said five of the restaurants are already being prosecuted while the remaining 30 are still being investigated.

Hu Da, a popular food chain in the greater Beijing area, is one of the establishments included in the CFDA's latest crackdown.

Hu Ling, the restaurant's general manager, said that they may have been unaware that some of the sourced seasoning that they were using contained traces of opiates. She has since decline to provide further comment.

Ground poppy powder is made from the plant's shells and capsules, which are known to have a higher content of opiates compared to the seeds that are often sprinkled on bagels.

According to a report by a local news agency, customers can easily purchase poppy powder for $60 a kilogram (2.2 pounds) from markets located in western China. The substance is often combined with chili oil and other powders so that it will be harder to detect without the use of laboratory equipment.

Police officials in Shaanxi province busted a noodle dealer in 2014 after having been tipped off by a botched drug test, while local authorities in Ningxia province closed down seven restaurants in 2012 after they discovered that the establishments were adding ground poppy powder to their food.

In 2004, 215 restaurants in Guizhou province were shut down for using the banned substance.

The Chinese government has pledged to enforce the ban on the use of illegal substances on food options. However, consumers in the country still face a number of well-publicized food scares such as gelatin-filled seafood, fake meat and fruits and even tainted baby formula.

In 2014, a Shanghai-based supplier to several big restaurant chains, such as Starbucks, KFC and MacDonald's, was discovered to have been selling expired and contaminated chicken meat to their clients.

Photo: Brian Jeffery Beggerly | Flickr