Lawmakers are burying the Obama administration with requests for information about a $400 million payment to Iran last January, despite administration attempts to stonewall the public on details of the payment.

The U.S. delivered $400 million in foreign currency, stacked on pallets in an unmarked plane, to the Islamic Republic in January, around the same time that Iran released three American hostages. Critics say the payment was for ransom, while administration officials have claimed that the timing of the transaction was "coincidental." The payment to the Islamic Republic is the first installment of a $1.7 billion legal settlement for a decades-old arms deal gone awry.

Kansas congressman Mike Pompeo is one of many lawmakers pressing for answers.

"President Obama must be straight with the American people, especially as he deals with the world's largest state sponsor of terrorism. For the administration to continue to refuse to answer simple questions regarding its suspicious delivery of $400 million in pallets of cash to Iran only raises more questions," Pompeo told THE WEEKLY STANDARD. "President Obama might not want to tell us how he circumvented the law, or broke it, but the American people deserve to know. I am working to make sure Congress does all it can to ultimately find out the truth."

Pompeo asked the State Department whether the payment was for ransom in January. After receiving an incomplete response months later, he and Texas senator John Cornyn introduced legislation that would force the administration to report the details of the payment to Congress.

Congressional committees and lawmakers have followed suit.

The House Committee on Oversight and Government Reform sent letters to the State and Treasury Departments requesting a timeline of the cash transfer and related documents. Both letters noted that while the president announced the prisoner release in January, he "did not mention" the $400 million shipment at that time.

President Obama has said that reports of the $400 million payment are "the manufacturing of outrage."

"We announced these payments in January. Many months ago," Obama said. "It was no secret."

His pronouncement has not quelled congressional concerns.

Iowa senator Chuck Grassley, chairman of the Senate Judiciary Committee, penned a letter to the Justice Department requesting records related to the payment after the Wall Street Journal reported that officials there expressed doubts about it.

He also reiterated concerns that the FBI reportedly "helped send substantial ransom payments to al Qaeda," and asked for records related to the law enforcement agency's involvement in the January prisoner swap.

"[The WSJ] reports are particularly troubling in light of the Department's continuing failure to cooperate with my inquiry into the FBI's alleged role in facilitating ransom payments to terrorist groups," Grassley wrote. "There are serious questions about this administration's policies regarding paying ransoms to terrorists and state-sponsors of terrorism."

Senator Tom Cotton of Arkansas sent his own letter to the Treasury and State Departments criticizing administration officials for refusing to disclose "the full nature and timing of the $400 million cash payment" to him for months, and requested specifics on how the remaining $1.3 billion would be paid.

A number of other senators also issued statements condemning the payment.

Administration officials have insisted that they were upfront with lawmakers.

"I can assure you that we don't do anything without notifying Congress, regardless of what that may be," State Department spokesman Mark Toner said last Wednesday. "We always make Congress aware of whatever actions we're taking."

The administration has also refused to disclose details of the agreement to the media.

Reporters have asked about the cash transfer at every State Department briefing since news of the payment broke. They've been met with insistence that "there's very little news to this."

Inquiries about how the payment was made have gone answered.

"I'm still frankly not prepared to talk about the mechanics," Toner told reporters last week.

The State Department agreed Tuesday when a reporter asked whether it would be a "waste of time" to continue looking for answers.

"Pretty much, yeah," spokeswoman Elizabeth Trudeau said. "I appreciate the question. As we've said, we're not going to get into a tick-tock."