About 30 passengers had left the bus when it was stopped and searched, apparently after a tip by an informant, the police said.
The passengers had left the Port of Galveston in Texas on Thursday for what was to be a four-day cruise to Cozumel, Mexico.
"But it can detect that certain passengers are experiencing stress," and a control panel can show which passengers have left their seat belts unfastened.
Indeed, that is the main limitation of these systems: flights are often delayed after most passengers have left for the airport.
The flight, carrying 254 passengers, had left the airport at 8 10 a.m. and was more than two hours into the flight when a pressurization problem forced it to turn around, passengers told The Los Angeles Times.
There was an armed guard at the harbour, and a full hour was allowed to elapse after the other passengers had left before Miss Mitford was brought ashore on a stretcher.
Shortly before the accident, the driver and seven passengers had left a nearby banquet hall, where an association of Nigerian immigrants had gathered from across the United States for a celebration that featured dancing and discussions about improvement projects they were sponsoring in their homeland.
Mr Andrews was seen urging people to get into the lifeboats, aware of just how little time the liner, thought to be unsinkable by many passengers, had left.
The duffel bags, which arrived on a flight from the Dominican Republic, were picked up by CBP after passengers had left the international terminal, reports ABC Philadelphia.
Finally, after all of the other passengers had left, little Sydney Jr., four years old, carefully walked down the steps, holding tight to the railing with one hand and grasping the hand of his three-year-old sister, Janet, in the other.
By the time screeners reviewed an image of the contents of the bag, the passenger had left the screening area with the bag, the station reported.
