A spokeswoman from Gate Gourmet, the Dutch caterer used by Delta, has said that the company is cooperating fully with investigators. Christina Ulosevich added that "details of this matter must remain confidential".
Gate Gourmet is a subsidiary of Swiss-based gategroup Holding AG, one of the largest independent global providers of airline passenger products and services.
More top news
Scientists find a cluster of spinal neurons integrate sensory data and unconsciously adjust muscles to maintain balance and avoid slipping.
Billionaire businessman Stefano Pessina has said the Labour leader's economic plans are "not helpful for business or the country."
British scientists believe their research may help to explain the missing material that makes up more than 80% of the universe's mass.