Eighty passengers and five crew members were held aboard a jet for three hours after it landed Saturday because a passenger said a man had dispersed a powdery substance in the ventilation system.

The substance was confetti from a greeting card that a man had accidentally spilled, FBI spokesman Andrew Black said.

Police, FBI and emergency crews met the plane at about 2:30 p.m. and set up a decontamination tent for the passengers of United Airlines Flight 1669 from Chicago. They were being released about 7 p.m.

"The substance being found in the airplane appears to be nothing more than confetti that spilled out of a greeting card," said FBI spokesman Andrew Black. "Now we have an airplane on the runway with 80 plus passengers who are not very happy right now."

The man's identity was not released, but Black said he is a longtime San Francisco Bay area resident.

Someone aboard the plane told a crew member the man had dispersed powder into the ventilation system. The San Jose airport was alerted, and once the plane arrived, fire department personnel took air samples from inside, said police spokesman Rubens Dalaison.

The man who spilled the confetti was escorted off the plane, stripped him of his clothing, washed down with detergent and dressed in a hazardous materials suit that traps vapors.

The man and the witness were questioned by police.

San Jose Fire Department battalion chief Kevin Conant said his department has been busy responding to numerous calls of mysterious powders.

"We've investigated everything from beach sand to baking powder to confetti," Conant said. "We're taking all these incidents seriously. We'll send all the resources required and investigate it as a credible threat."

At Washington's Dulles International Airport, a spokeswoman said a powdery substance found in a restroom on a United Airlines plane from London was being tested at an Army laboratory in Maryland.

Spokeswoman Tara Hamilton said the flight was met Saturday by a hazardous materials team and FBI agents, who determined that 17 people out of 216 passengers and 14 crew members had used the bathroom.

The 17 passengers were detained and preliminary decontamination steps were taken on them, which Hamilton said consisted for most part of washing their hands.