House Speaker Paul Ryan on Wednesday demanded a full explanation from the Obama administration on how it decided to fly $400 million in cash to Iran in the midst of a hostage crisis earlier this year.

"If true, this report confirms our longstanding suspicion that the administration paid a ransom in exchange for Americans unjustly detained in Iran," said Ryan, R-Wis. "It would also mark another chapter in the ongoing saga of misleading the American people to sell this dangerous nuclear deal. Yet again, the public deserves an explanation of the lengths this administration went to in order to accommodate the world's leading state sponsor of terrorism."

The Obama administration on Wednesday was defending the transaction as a move to pay Iran back the money it gave the U.S. in 1979 as part of an arms deal that never went through after the Shah of Iran was overthrown. But Republicans were asking questions about the timing of the payment and whether it's related to the release of four Americans who were detained in Iran, but were released when the cash was sent.

Some were also saying sending cash will only make it easier for Iran to fund terrorist organizations, and harder for the U.S. to trace those payments.

"Wooden pallets stacked with euros, Swiss francs and other currencies were flown into Iran on an unmarked cargo plane, according to these officials," the Wall Street Journal reported Tuesday. "U.S. officials also acknowledge that Iranian negotiators on the prisoner exchange said they wanted the cash to show they had gained something tangible."

Other Republicans also criticized the report by saying it appears to be a ransom payment to Iran, despite the Obama administration's claim that it doesn't pay ransom for the return of hostages.

"By continuing to kowtow to the world's leading state sponsor of terrorism, all while trying to hide their actions from Congress and the American people, the Obama administration will only put more lives at risk along the way," Rep. Diane Black, R-Tenn., said Wednesday. "Americans deserve a commander in chief who will fight to destroy hostile Islamic regimes, instead of paying them off as this president has done."