Delta Air Lines is working with investigators in the US and the Netherlands after objects that appeared to be sewing needles were found in sandwiches on four flights from Amsterdam to the US yesterday.

One person was injured and declined medical treatment after a flight landed in Minneapolis, Kristin Baur, a Delta spokeswoman, said in an interview today. The incident is being investigated by the US Federal Bureau of Investigation and officials in the Netherlands as well as Gate Gourmet, Delta's caterer, she said.

"Delta is taking this matter extremely seriously and is cooperating with local and federal officials who are investigating the incident," Baur said.

In addition to the Minneapolis case, single needles were found in a sandwich by a federal air marshal on a flight to Atlanta, by a passenger on a separate flight to Atlanta and in a sandwich that hadn't been served on a plane to Seattle, Baur said. She didn't know the extent of injury to the Minneapolis passenger.

After the discovery, Delta removed items prepared at the Gate Gourmet facility in Amsterdam and replaced them with pre- packaged foods. It pulled from the menu turkey sandwiches, which were served to customers in business class on the flights.

The sandwiches were prepared by Gate Gourmet, said David Fisher, a spokesman. He declined to comment further on specifics of the incidents because they are under investigation.

"We take this terribly upsetting situation very seriously," Fisher said. "We immediately launched an investigation into this incident and are working in full cooperation with the authorities that are involved."

No other incidents were reported on flights from Amsterdam to the US yesterday or today, Baur said. Atlanta-based Delta operates as many as 18 such flights daily, and flew 17 yesterday.

Gate Gourmet, the largest independent provider of catering and provisioning services for airlines and railroads, is a unit of Gategroup Holding AG, based in Zurich.