By CBS3 Staff

UPPER DARBY, Pa. (CBS) – A lockdown at Upper Darby High School has been lifted following a text message threat, Thursday morning. The school was placed on lockdown around 9:30 a.m. and police were called to the school on Lansdowne Avenue.

Upper Darby police say there is no active threat and students and staff are all safe. The lockdown was lifted at 10:23 a.m.

Police say students were included in a thread of text messages about a possible threat to the school. According to authorities, the text was sent by a student from another school in a different community.

No Upper Darby student was involved in making the threat.

There will not be an early dismissal and after-school activities will resume as usual.

The incident remains under investigation.