(AMSTERDAM) -- After six needles were reported in sandwiches served on Delta flights from Amsterdam, the FBI and Dutch police are investigating an in-flight caterer and potential security gaps as the food was transferred from the caterer's facility at Schiphol airport to the planes, ABC News has learned.
The six needles were reported on four separate flights to three separate cities on Sunday, federal law enforcement officials said. Those officials said that two people were slightly injured and treated by Emergency Medical Technicians. Delta acknowledged one person was injured, and treated at a hospital.
The sandwiches were prepared in the kitchen of the Gate Gourmet catering company at Schiphol. Gate Gourmet operates in 28 countries and serves an average of 9,700 flights every day of the year -- and over 300 million passengers annually.
In a statement, Gate Gourmet said, "We take this matter very seriously. Gate Gourmet immediately launched a full investigation to determine the root cause of this disturbing incident, and we are treating this as a criminal act."
Authorities noted that two victims were a father and a teenage son who were traveling on separate flights from Amsterdam to the United States. The father was flying to Minneapolis/St. Paul and the son to Atlanta.
The five needles that were recovered from the six reported incidents are being tested for biochemical hazards but so far there is no indication that they were tainted. The sixth needle was discovered by a federal air marshal who tossed it and his sandwich in the trash.
Dutch police are the lead investigators, and they are being assisted by the FBI, because U.S. citizens were victims of what is being called a criminal act.
Authorities are calling this a potential act of sabotage and remain deeply concerned that the tainted sandwiches found their way onto four separate flights to Atlanta (2), Minneapolis and Seattle.
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