Dancers serve free sample of McDonald's ice cream desert 'McFlurry' at a launching event in Tokyo April 19, 2007. Getty Images/ YOSHIKAZU TSUNO

Pictures of the insides of a McDonald’s McFlurry machine posted by a former employee has gone viral, earning them thousands of retweets and likes and giving lovers of the fast food chain something to worry about.

The employee, who goes by the name of "Nick" on Twitter posted a series of stomach-churning photos on July 18 after he was fired from his job.

McFlurry is an ice cream product made by McDonald's, and is a favorite among fast food lovers across America. However, the pictures posted by Nick made even McDonald's loyalists think twice about the conditions in which their much-loved dessert was being made.

Nick began by posting side-by-side snaps of the unpleasant residue left behind on a metal tray inside the McFlurry machine after the customers have been served their orders. The pictures showed a slender tray filled with greenish-grey slime and dirt.

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It is not clear to which McDonald's outlet the pictures were taken since Nick didn't provide any details along with the snaps. The only point of reference is the fact that Nick lives in Louisiana.

The pictures sparked off a long debate in the comment section of the post. While half the people blamed employees like Nick for not doing their job properly and keeping the insides of the machines clean, the other half was pretty sure it was the job of the management and not the employees to clean big machines like the one used for making McFlurries. Nick put an end to the debate by stating it was typically the manager of the establishment who was in charge of cleaning the particular machine.

There were also some who wondered if the fired employee was trying to get back and tarnish the name of his employer by posting fake pictures. Nick replied to this strain of questioning by posting a few more pictures, which demonstrated that the machines from where their frozen desserts arrived appeared clean on the outside but is caked with grease on the inside.

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The first one was a side-photo of the seemingly spotless machine that Nick has pulled out the tray from. The second picture was of a greasy spatula that the kitchen staff in the outlet used.

Nick then went on a roll, claiming he might as well expose other questionable facets of the company while he was on it. The former employee posted a number of pictures of the dirty kitchen floors and processed meat served by McDonald's in their burgers, stating the patties were not even made of "real meat or fish."

McDonald's has been embroiled in controversies a number of times in the past, mostly due to its lack of hygiene in the preparation and storage of foods. In an investigation conducted by a BBC watchdog show a week back, traces of fecal matter were discovered in the ice of three branches of McDonald's in the United Kingdom, Metro reported. The same bacteria was also discovered in samples taken from six outlets of Burger King and seven branches of KFC.