WRAY, Colo. (AP) — Schools are closed for a second day in Wray as authorities investigate a possible threat that was made using the social media app Yik Yak.

Wray police said Friday that they have interviewed several students and staffers to try to identify who made the post and have been in contact with Yik Yak. The app allows users to send messages anonymously within geographic areas and has been used before to make threats against schools and individuals.

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Police searched the eastern Colorado city’s schools but say they found nothing to cause alarm.

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Schools in Wray and nearby Idalia were closed Thursday after police learned about the post. Idalia superintendent Tim Krouse says he felt it was reasonable to reopen the town’s only school.

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