A Burger King in Brooklyn, New York, had been passing off beef burgers as Impossible Whoppers - a vegan version of its signature Whopper - to customers.

Eater New York reports that for several weeks, the store has been replacing Impossible Whoppers requested in Seamless delivery orders with regular Whoppers.

A delivery-person was then allegedly asked to tell the customer about the switch.

But customers told Eater that not only did their drivers not say anything, their receipts listed orders as an 'Impossible Whopper'.

The Impossible Whopper - a vegan version of Burger King's signature Whopper - had been advertised on a Brooklyn-area Burger King's Seamless page since May 20

The Impossible Whopper - which uses a plant-based patty from Impossible Foods - is meant to target both vegetarians and meat-eating customers who want a more balanced diet.

In April, the burger chain began testing the new sandwich in certain locations in St Louis, Missouri.

Last month, Burger King announced it will be offering the burger in all of its stores by the end of the year. However, it's currently not available in New York.

According to CNN, the plant-based patty is only available at certain stores in Montgomery, Alabama; Miami, Florida; Columbus, Georgia; and St Louis, Missouri.

One Williamsburg resident, who asked that he not be named, told Eater that he ate two burgers before realizing he wasn't eating the Impossible Burger.

'I was incredulous,' he told the site. 'It's maybe 20 percent poisoning. This is a city where there are a lot of reasons why people don't eat [meat], from religion to health to ethics.

Impossible Whoppers are only available at stores in Montgomery, Alabama; Miami, Florida; Columbus, Georgia; and St Louis, Missouri. Pictured: The Brooklyn Burger King that was switching orders

Eater took a screenshot of the Brooklyn Burger King's Seamless page advertising that it sold the Impossible Whopper, which has since been taken down.

At one point, the vegan burger was rated as the store's most popular item on Seamless.

It's unclear how long the chain had been advertising the burger, but it had been at least since May 20 of this year.

It also is unknown how many customers were affected by the burger swap.

Social media users flocked to Twitter in droves to comment on the incident

'The Impossible Whopper is not yet available in New York, but we look forward to making it available for our guests soon,' a Burger King spokesperson told DailyMail.com.

'We have recently become aware that due to a technology error, one of our franchisees incorrectly listed the Impossible Whopper as a menu item available at some New York-area restaurants through two third-party delivery platforms.

'The issue has been corrected and the item is no longer listed as an option until we officially bring the Impossible Whopper to New York. We apologize for any confusion this has caused.'

According to the statement, anyone with questions has been asked to call (866) 394-2493.

Social media users flocked to Twitter in droves to comment on the incident.

'WTF...this is really bad!!' tweeted on user.

'Kind of amazed the folks at the BK are claiming they thought substituting an Impossible Whopper with a regular Whopper would ever be acceptable' wrote another.

GrubHub, Seamless's parent company, did not immediately reply to DailyMail.com's request for comment.