After the White House affirmed that President Donald Trump will not release his tax returns this year, Sen. Elizabeth Warren (D-Mass.) argued on Tuesday that “the issue is not over” and urged Americans to continue voicing their concerns about the president’s lack of transparency.

“Look, why is the case that people at the very top should get a bunch of tax breaks, should be able to hide their business dealings when everybody else pays, everybody else gets out there and makes our roads and bridges work, makes our schools work?” she told NBC’s “Today” show. “Let’s see what Donald Trump is up to.”

WATCH: “The issue is not over. He promised during the campaign that he would reveal his taxes.” @SenWarren on Trump tax returns pic.twitter.com/IlxJtbsbY2 — TODAY (@TODAYshow) April 18, 2017

Over the weekend, thousands of protesters around the country participated in marches tied to the tax filing deadline, demanding that Trump release his tax returns. Trump has repeatedly refused to do so, falsely claiming that he cannot because he is under IRS audit.

“I don’t know,” Warren said, when asked if Trump would ever disclose his tax information. “But I’ll tell you this, I think that people are going to keep demanding it, and they are going to keep demanding it and making their voices heard on this.”

After initially promising to release his tax returns during the presidential campaign, Trump repeatedly avoided doing so and became the first president in four decades to not make his tax information public.

White House press secretary Sean Spicer again claimed on Monday that an IRS audit is keeping Trump from releasing his tax returns. But the revenue service has said that “nothing prevents individuals from sharing their own tax information.”

Both Trump and his administration have argued that the issue is settled because he won the election without having released the information.

I did what was an almost an impossible thing to do for a Republican-easily won the Electoral College! Now Tax Returns are brought up again? — Donald J. Trump (@realDonaldTrump) April 16, 2017

After repeated questions from reporters about the issue, Spicer demurred on Monday when asked if it was safe to say that Trump will not release his tax returns at all.

“We’ll have to get back to you on that,” Spicer said.