New York, New York - Sandwich giant Subway is facing claims that the tuna salad used in its sandwiches and wraps doesn't actually contain any tuna.

But what is in the tuna sandwiches if it's not tuna?

According to a lawsuit filed with the US District Court for the Northern District of California by two customers named Karen Dhanowa and Nilima Amin, the filling is "a mixture of various concoctions that do not constitute tuna, yet have been blended together by defendants to imitate the appearance of tuna."

Multiple labs examined Subway's "tuna" and allegedly found no traces of the fish, nor any traces of fish at all.

Dhanowa and Amin are suing the fast food chain, saying they "were tricked into buying food items that wholly lacked the ingredients they reasonably thought they were purchasing," the Washington Post reported.

Subway denies the claims, asserting they use wild-caught tuna in their products, as advertised on their website.

Speaking to the Post, a spokesperson to the company said, "Tuna is one of our most popular sandwiches. Our restaurants receive pure tuna, mix it with mayonnaise and serve on a freshly made sandwich to our guests."

The latest lawsuit comes just months after an Irish judge found that Subway’s bread could not legally be considered bread, due to its sugar content.