The head of the national security division at the Justice Department was among the agency’s senior officials who objected to paying Iran hundreds of millions of dollars in cash at the same time that Tehran was releasing American prisoners, according to people familiar with the discussions.

John Carlin, a Senate-confirmed administration appointee, raised concerns when the State Department notified Justice officials of its plan to deliver to Iran a planeful of cash, saying it would be viewed as a ransom payment, these people said. A number of other high-ranking Justice officials voiced similar concerns as the negotiations proceeded, they said.

The U.S. paid Iran $400 million in cash on Jan. 17 as part of a larger $1.7 billion settlement of a failed 1979 arms deal between the U.S. and Iran that was announced that day. Also on that day, Iran released four detained Americans in exchange for the U.S.’s releasing from prison—or dropping charges against—Iranians charged with violating sanctions laws. U.S. officials have said the swap was agreed upon in separate talks.