Washington (CNN) A $150,000 payment to President Donald Trump's foundation in 2015 by a Ukrainian billionaire is being examined by special counsel Robert Mueller's team, The New York Times reported Monday, citing three people briefed on the matter.

The donation was made by Victor Pinchuk in September of that year, according to the Times' report, and in return Trump made a 20-minute video appearance that month at a conference in Kiev.

The payment, which was the largest donation to the charity in 2015 aside from donations from Trump, was discovered when investigators subpoenaed the Trump Organization for information related to foreign business deals, according to The New York Times.

Mueller is leading the investigation into Russian meddling in the 2016 US presidential election, which includes examining any potential ties between Trump campaign associates and Russia. Trump has repeatedly denied any collusion.