Dutch military police are investigating how apparent sewing needles were present in food on four U.S.-bound Delta Airlines flights from Amsterdam on Sunday.

The needles were found in sandwiches made by the airline's Amsterdam caterer, Gate Gourmet.

One passenger on a flight to Minneapolis was injured by a needle but declined medical treatment.

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

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

Caterer Gate Gourmet said the company was cooperating fully with investigators but declined to give further comments.

Sarah Sheffer, Reuters