Yale University announced Monday it was on lockdown following reports of an armed person on the loose at one of the most prestigious universities in the United States. A series of alerts on its website ordered all staff and students to shelter in place until further notice, as teams of police scoured the sprawling campus in New Haven, Connecticut for the presumed assailant. There was no confirmation of any injuries or shots fired. New Haven police received an anonymous call reporting the person with a gun shortly after 10:00 am (1500 GMT). The university recess for the Thanksgiving holiday began over the weekend. Yale has more than 14,000 students and a teaching staff of more than 9,000. It was established in the early 18th century and is one of the top universities in the US prestigious Ivy League.