Dollar Tree Inc. (DLTR - Get Report) may have a big backer in billionaire activist investor Carl Icahn, and that is sending the stock higher Tuesday, Oct. 16.

Dollar Tree shares were up nearly 6% Tuesday after the New York Post reported that Icahn has been quietly building a stake in the struggling discount retailer. The stock has fallen about 25% year to date.

Icahn's General Counsel Jesse Lynn declined to comment on the New York Post story, and told TheStreet that he didn't know where the Post got its story from.

This isn't Icahn's first foray into the dollar retail space. In 2014, Icahn built a large stake in Family Dollar before pressuring the company to find a buyer. That buyer would eventually be Dollar Tree, which paid $8.5 billion for the company. Icahn's firm reportedly made a profit of about $200 million from the deal.

Dollar Tree acquired Family Dollar in 2015.

Last week, Dollar Tree announced plans to hire 25,000 associates in a nationwide hiring event scheduled for Wednesday, Oct. 17.

"I am so proud of the progress we are making within our Dollar Tree and Family Dollar brands on developing and retaining engaged associates as we continue to invest in our talent," said Chief Human Resources Officer Betty Click.

TheDeal's Ronald Orol contributed to this story.