A Homeland Security Department official said all the machines will be installed by the end of June, but spoke on condition of anonymity because the announcement has not been made publicly.
Officials first disclosed the body scanners were coming in December 2009, but did not reveal the timing.
The scanners are a key part of the Obama administration's airport security plans. Obama called for more scanners to be deployed after the attempted bombing on Christmas Day, but Chicago's scanners had been planned well in advance of that event.
The body scanners have been the subject of much controversy due to their imaging technique, which reveals a full-body silhouette, including what some might consider unattractive or embarassing anatomical features.