The Detroit News reports a canine alerted police to something in the man's carry-on luggage, prompting authorities to question and search him before releasing him.
Ronald Smith, chief U.S. Customs and Border Protection officer for the Detroit area, in an e-mail to the News, apologized that accurate information on the incident had not been available earlier, the newspaper reported.
After a couple aboard the flight reported seeing someone other than terror suspect Umar Farouk Abdulmutallab being handcuffed, Smith initially had said the second person was from another flight.
In his e-mail, copied to the couple, Kurt and Lori Haskell of Taylor, Smith said he had received new information and hoped it would "clear up the matter."
The couple said the man, who appeared to be of Indian descent, was taken into a room for questioning and later came out handcuffed.
The man was interviewed and searched but not arrested, Smith said.
Abdulmutallab, a 23-year-old Nigerian who claims ties to al-Qaida, was charged with attempting to ignite an explosive on the Dec. 25 flight bound from the Netherlands to Detroit.