Federal law enforcement officials are investigating a U.S. Navy veteran's claims that Rep. George Santos, a New York Republican, took money raised for a lifesaving surgery for his dying dog.

The U.S. Attorney's Office in the Eastern District of New York is conducting an investigation into Santos' finances. The veteran, Rich Osthoff, spoke with two FBI agents on behalf of the U.S. Attorney's Office and handed over text message exchanges with Santos.

Santos has not responded to questions about the matter and a spokesperson for the U.S. Attorney's Office declined to comment.

Osthoff had previously told CNN that in 2016 Santos promised to raise funds for his pit bull, Sapphire. At the time, Osthoff was homeless and living in a tent after losing his job and house. Santos set up a GoFundMe account that raised around $3,000. However, Osthoff claims that Santos became uncooperative when he tried to access the funds.

Text messages provided by Osthoff to CNN show the exchanges between him and Santos in 2016. In the messages, Osthoff asks Santos if he had made contact with the vet and Santos replies that he just called and is jumping through hoops.

"Hey Anthony, Rich here. I was hoping to hear from you. Just checking whether you made contact with the vet," Osthoff writes in one text to Santos, who was going by the name Anthony Devolder at the time.

Santos replies that he "just called" Osthoff and he's been "jumping through hoops." He adds, "They are not as flexible as you said they were," apparently speaking about the vet Osthoff referenced.

Santos also writes that a vet had ruled out the surgery but he would take the dog to a vet for an ultrasound. After Osthoff expressed concerns about being "mined" for donations, Santos told him that the funds would be moved to the next animal in need and used to keep Sapphire comfortable.

"I'm starting to feel liked [SIC] I was mined for my family and friends donations," Santos tells him that, because his dog is not a candidate for surgery, "the funds are moved to the next animal in need and we will make sure we use of [SIC] resources to keep her comfortable!"

In January, Santos told CNN that he had no knowledge of what Osthoff was referring to and defended his work with animals.

Politico first reported the news.

The investigation is ongoing.