The New England Patriots are apologizing after charging fans for tap water at Gillette Stadium on Sunday.

Numerous fans tweeted their frustration after they were charged $4.50 for tap water at stadium concession stands.

Temperatures for the Patriots' game in Foxborough against the Houston Texans reached 86 degrees.

The Boston Globe reports that the stadium doubled its inventory of water bottles for the average "hot" game and had four times the inventory of an average game, but many stands still ran out.

As the stands ran out of water bottles, fans say they had to buy tap water in soda cups for $4.50. The concession stands did not provide complimentary water cups.

“We apologize. That should not have happened. It is the first time that I have ever heard that complaint here. We are looking into the matter to ensure that it doesn’t happen again,” New England Patriots spokesperson Stacey James said, according to the Boston Globe.

Angry Patriots fans took to Twitter, some calling it price gouging.