Delta Air Lines says it is working with United States federal authorities after what appeared to be sewing needles were found in food on four US-bound flights that left from Amsterdam last weekend.
The needles were found in sandwiches made by the airline's Amsterdam caterer, Gate Gourmet.
One person on a flight to Minneapolis was injured but declined medical treatment.
Both the FBI and Dutch officials are investigating.
A spokesperson for the catering group says it is co-operating fully with investigators.