Prime Minister David Cameron has called the horsemeat scandal an "appalling situation", stressing that if criminal activity has taken place "there should be the full intervention of the law".
Speaking at Prime Minister's Questions, Mr Cameron said an enhanced testing regime not only found contamination, but discovered that in some instances horsemeat had been passed off as beef.
He called the discovery "completely unacceptable".
More top news
The Queen was joined by the Prime Minister, who will visit the battlefields on Friday.
The teen was stabbed as she slept in her bed in the West Bank in Israel.
Transgender US service members will be able to serve openly and cannot be discharged on the basis of their gender identity.