The Obama administration secretly gave Iran $400 million around the same time four American prisoners were released in mid-January, the Wall Street Journal confirmed late Tuesday.

The cash — euros, Swiss francs and other currencies packed in wooden pallets — was airlifted to Iran in a discrete operation by government officials, according to U.S. and European officials who were briefed about the move afterward.

The Journal said the payment was the first installment of a $1.7 billion payment to Iran to resolve a fight over an arms deal from 1979.