North Korean officials handed a $2 million bill for medical expenses for now-deceased Otto Warmbier in 2017, CBS News' Christina Ruffini reports. Joseph Yun, the special envoy to North Korea at the time, signed off on paying the bill, but the U.S. did not intend to pay it.

A former State Department official said the incident was not really a secret, and the invoice remains unpaid.

Warmbier was detained in January 2016 at the end of five-day tour in North Korea. He was sentenced to 15 years hard labor for allegedly stealing a propaganda banner at his hotel. Brain scans taken by the North Koreans indicated that he suffered severe injuries to his brain shortly after his conviction in March 2016. He was comatose when he was released by the regime in June 2017 and died a few days after his arrival at home in Ohio.

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The Washington Post first reported the $2 million bill, and reported President Trump had agreed to take the necessary steps to secure Warmbier. The Post reported that Yun was handed the bill when he and a doctor traveled to North Korea to transport Warmbier back on a medical evacuation plane. The White House is declining to comment on the matter.

"We do not comment on hostage negotiations, which is why they have been so successful during this administration," White House press secretary Sarah Sanders said in a statement to CBS News.

The president sparked intense backlash after his last visit with North Korean Kim Jong Un for the unsuccessful summit in Vietnam, when he told reporters he believed Kim when the dictator said he was unaware of Warmbier's condition.

"He tells me he didn't know about it, and I take him at his word," the president said at a press conference in Hanoi in February.

Since Mr. Trump met with the dictator for the first time last year, the president has softened his stance on Kim, whom he used to disparage as "little rocket man." Mr. Trump has praised the "love letters" from Kim, and lauded his accomplishments.

The president has taken pride in claiming the U.S. didn't pay for hostages returned from North Korea to the U.S.

"Kim Jong Un did a great service to himself and to his country by doing this. But those hostages came out, with respect, we didn't pay for them," the president said during an Indiana rally in May 2018, after the return of three hostages back to the U.S.

"What he did was the right thing, but they came out for nothing and the others came out for $1.8 billion in cash," the president said in 2018.

Fin Gomez and Kathryn Watson contributed to this report.