Sabrina Carpenter canceled her Portland, Ore., concert Monday night (April 10) due to "unforeseen circumstances," which have now been revealed by local police.

According to Rolling Stone, Carpenter was forced to cancel following a "credible security threat" to the venue where she was originally scheduled to perform.

"Employees with the Crystal Ballroom called after they received a phone call from an anonymous person claiming they were going to blow up the venue," Portland Police Bureau Lt. Nathan Sheppard told Rolling Stone.

"While the threat was not directed at Keller Auditorium specifically, Sabrina and event organizers agreed that out of an abundance of caution, the show be called off. Steps were taken to ensure that the audience exited the venue calmly, quickly, and safely," an AEG Presents spokesperson added.

READ MORE: Sabrina Carpenter Faces Backlash Online for Onstage April Fool's Joke

Police reportedly sent out extra patrols to both venues as a precaution but found no explosives.

"Portland – I can’t tell you how much it breaks my heart, this is the last thing I wanted to do, but due to unforeseen circumstances, we will not be able to perform tonight," the pop star tweeted early Tuesday morning.

"You will be refunded," she assured fans, noting that her team is working on rescheduling the concert.

Carpenter's concert was originally supposed to take place at Portland's Crystal Ballroom, but had been upgraded to a larger venue, the Keller Auditorium, where fans were eventually asked to leave for their safety.

Fans were apparently able to participate in Carpenter's VIP soundcheck event and watch opening act Spill Tab before being asked to exit the venue.

In a tweet documenting the experience, a venue staff member can be heard announcing the cancellation, saying, "Due to unforeseen circumstances, Sabrina will not be able to perform tonight," as the crowd gasps.

Billboard reports that a clear bag policy was implemented at Carpenter's Seattle show Tuesday night.

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