FBI and Transportation Security Administration agents gave no specific reason for the action and said no arrests were made as all 247 passengers on board the Boeing 747 jet were allowed in.
"There were a number of passengers on that British Airways flight that law enforcement officials wanted to speak with," said an FBI spokeswoman who asked not to be named.
Homeland Security Department spokeswoman Rachael Sunbarger was quoted as saying the flight had been detained on the tarmac for screening, but she gave no further details.
In London, a British Airways spokesman said the carrier had no idea why the investigation took place.
"The FBI directed that the airplane be parked at a remote area and proceeded to interview all of the passengers," spokesman John Lampl said. "We do not know what triggered this investigation."
He said all of the passengers had completed the interview process about three hours after landing and the plane was towed to its normal gate to prepare for a return flight to London.
The incident comes amid heightened security precautions as the United States raised the "terror alert" to its second highest level 10 days ago, citing the possibility of "terror" attacks over the Christmas and New Year holiday period.
Last week, six Air France flights between Paris and Los Angeles were canceled when US intelligence warned French authorities that the passenger lists included suspicious names.