NEW YORK (Reuters) - Delta Air Lines Inc said it was working with federal authorities after what appeared to be sewing needles were found in food on four U.S.-bound flights that left Sunday from Amsterdam, injuring one passenger.

The needles were found in sandwiches made by the airline's Amsterdam caterer, Gate Gourmet, Delta spokeswoman Chris Kelly said in an email Monday. The FBI and Netherlands officials are investigating, Delta said.

"Delta is taking this matter extremely seriously and is cooperating with local and federal authorities who are investigating the incident," the airline said in a statement.

"Delta has taken immediate action with our in-flight caterer at Amsterdam to ensure the safety and quality of the food we provide onboard our aircraft," the statement said.

One person on a flight to Minneapolis was injured but declined medical treatment.

A suspected sewing needle was also found in a sandwich by a passenger on an Atlanta-bound flight. A U.S. air marshal found another while flying on another Atlanta-bound flight.

Another apparent needle was found aboard a Seattle-bound flight in a sandwich that had not been served.

Gate Gourmet is a subsidiary of Swiss-based gategroup Holding AG, one of the largest independent global providers of airline passenger products and services.

Christina Ulosevich, a gategroup spokeswoman, said the caterer was cooperating fully with investigators. She declined to comment further, saying "details of this matter must remain confidential."