By Hayley Peterson, Business Insider

McDonald’s is under fire from customers accusing the burger chain of serving mozzarella sticks that are missing a key ingredient: cheese.

Customers are posting pictures of hollowed-out mozzarella sticks online and accusing the burger chain of serving them “fried air.”

McDonald’s launched mozzarella sticks nationwide this month as part of a new “McPick 2” promotion, which allows customers to pick two of the following for $2: a McDouble, a McChicken, small fries, and mozzarella sticks.

The mozzarella sticks are also available on their own, costing $1 for three sticks.

But photos posted online seem to show that for many customers, all three of the mozzarella sticks in their orders were missing a cheese filling.

When we tried some mozzarella sticks in November, all three sticks in our order contained cheese.

McDonald’s did not immediately respond for comment.

User @Heyamber021 tweeted this photo and comment, “Craving mozzarella sticks. Excited that @McDonalds has them! Just to get home to have hollow breading :( #sad “

(@Heyamber021/Twitter)

Another user, ‏@neongypsyx, posted a similar image and said, “I got mozzarella sticks from @McDonalds for the first time and there was no cheese never going back again lol”

(Photo: @neongypsyx/Twitter)

Danielle, aka, @CheeseburgerCas, posted another photo with this comment, “@McDonalds I when I order mozzarella sticks I generally want some cheese.”

From @RaisinBran66: All 3 of @McDonalds new Mozzarella Sticks came empty. #wheresthecheese #donttrythisitem:

(Photo: @RaisinBran66)