The men, who were in two boats, were reported missing late Sunday by the U.S. military in Kuwait.
On Monday, the Iranians released the four soldiers, the civilian contractor and the boat captains. They were located by a U.S. patrol craft on the Shatt Al Arab.
"They've been recovered safely," U.S. Air Force Capt. Jeffrey Sandrock, a Central Command spokesman, told CBS Radio News. "Initial medical examination of the returned personnel indicates they sustained no injuries, nor were there any signs of physical abuse."
Sandrock identified the seven released as "four soldiers from the U.S. Army's 1092nd Engineer Company and a U.S. Army contractor from Kellogg, Brown and Root, and two civilian boat captains."
In Tampa, Florida, the U.S. Central Command said the boats were taking the oil company personnel to the Mini al Bakr platform to conduct a survey, when they were stopped by the Iranians who blindfolded them and took them to a building where they were interrogated.
"We're checking to see exactly what the circumstances were but initial indications are that they had strayed into Iranian waters," said Sandrock. "At this point, the indications are that the Iranians acted fully within their authority."
The Mini al Bakr platform is very close to Iran's declared international water boundaries. The incident occurred near the al Faw peninsula on Iraq's easternmost tip.
Control over the Shatt al Arab waterway was the main reason for the bloody eight-year war between Iran and Iraq in the 1980s.
So far, there have been no incidents between the Iranians and U.S.-led-coalition forces that occupied Iraq in April.