Eighty passengers were given decontamination showers, 500 were locked in rooms without water or toilets, and flights were delayed for hours after a substance that appeared to be curry powder was discovered at Australia's Adelaide Airport yesterday.

The yellow powder was found on the bags of passengers who had just disembarked from a 7.30am Singapore Airlines flight.

The scare resulted in more than 500 passengers from three international flights being kept in rooms without toilets, few chairs and no water for up to six hours while emergency response teams investigated the source and nature of the powder.

While airport staff were pleased with the way the incident was handled, passengers complained about being held without any amenities and called the process a disgrace.

North Adelaide resident Henry Botha, who arrived on a Qantas flight from Singapore, said people resorted to urinating in plastic bottles.

"It was a total disaster. No one seemed to manage the show," Mr Botha said.

One official told Mr Botha the powder looked "awfully like and smells awfully like curry powder".

Peter Baverstock, of the Barossa Valley, north of Adelaide, was one of the 80 people to find the powder on their bags.

"After a couple of hours, we asked if we could have some water and there were no chairs and then we asked if we could have something to eat," he said.

"I thought Osama bin Laden must be having the last laugh, when a bit of powder can shut down an international airport."

Mr Baverstock said the substance was still on his luggage when he left the airport.

Almost six hours after the 7.30am flight landed, the passengers were allowed to leave.

Richard Gray, of the Metropolitan Fire Service, said up to 80 passengers had contact with the substance and were given decontamination showers.

"There was a number of bags that were coated in it and when passengers were lifting them off the conveyor belt, that's when Customs officials became aware of it and enacted hazard-control activities," Mr Gray said. The airport fire service decontaminated the plane's cargo hold and conveyor belts before people were allowed on the plane for a return flight.

Adelaide Airport spokesman John McArdle said it would take up to a week to determine what the substance was.