Delta Air Lines Inc. and the FBI are trying to figure out the reason behind this accident in which one passenger on a flight to Minneapolis was injured.

The airline told The Associated Press that what appeared to be sewing needles were found in sandwiches Sunday.

The injured passenger declined to get medical attention, according to Delta spokeswoman Kristin Baur. The other needles were on two flights to Atlanta and one to Seattle.

Another sandwich served on the Minneapolis-bound flight also had a needle, according to Baur.

The FBI's Atlanta office has opened a criminal investigation into the matter, the agency reportedly stated in a written statement.

The flight attendants stopped serving the sandwiches as soon as the needle was discovered. Pizza was served instead.

Messages went out to other flights on the Amsterdam route, where the sandwiches had been prepared by a catering company.

The sandwiches were made in the Amsterdam kitchen of catering company Gate Gourmet, and were to be served to business class passengers on Delta flights.

Baur said security for its meal production has been increased and it is using more pre-packaged food while the investigation continues.

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

Gate Gourmet spokeswoman Christina Ulosevich said the company rubbished the talks of needle in the sandwich and confirmed that they had gotten no reports of similar incidents on any of the other airlines it serves out of Amsterdam.

She said the company did not yet know how the needles got into the sandwiches.

Gate Gourmet said in a statement, "We take this matter very seriously, and we have launched our own full-scale investigation." It also said it was "heightening our already stringent safety and security procedures, to prevent any recurrence."