Donald Trump filed for an extension to submit his 2016 tax returns, NBC News reported Saturday citing a White House official, the latest reminder that the billionaire president continues to break with tradition and has not released his tax history.

Interest in Trump's tax returns, a factor during his campaign for the White House, has grown as Congress and the FBI investigate the Trump administration and campaign's possible ties to Russia.

Critics, including some Democratic lawmakers, have demanded Trump release the information to prove there are no financial entanglements that create conflicts of interest. Trump's personal lawyers said in a letter that his returns from the past 10 years show that — with a few exceptions — he received no income from Russian sources and owed no debts to Russian lenders.