People in Austin, Round Rock, San Marcos and Bastrop on Thursday received dozens of bomb threats by email and phone, according to police officials.

Police have not found any bombs. Investigators believe the threats are not credible and are working to find out where they came from, Austin, Round Rock and Bastrop police said.

Authorities in New York City, Oklahoma City, Boston, Orlando, Flo., and other cities responded Thursday to numerous bomb threats, with some officials choosing to evacuate facilities. Columbine High School in Colorado received a false bomb threat, causing the school and 22 others nearby to be placed on lockdown, according to NBC News.

Austin police responded to 24 calls for service at various locations regarding email bomb threats, and Round Rock police received reports of eight bomb threats sent by email to businesses and organizations, police said.

The San Marcos Regional Airport also received an emailed bomb threat that was deemed not credible, San Marcos city officials said.

The email targeting the San Marcos airport said an explosive had been hidden in the building and that the device would be detonated if officials evacuated or if police responded. The email also demanded a payment be made via cryptocurrency, San Marcos officials said.

Blue Skies Aviation employees were asked to evacuate, and officers performed a cursory sweep of the location, San Marcos officials said. No suspicious items were located and the business returned to normal operation.

Bastrop police said they responded to an email bomb threat at the Lost Pines 8 Movie Theater at 1600 Chestnut Street. The owner of the business told police the threat said an explosive device had been placed inside the property. Police said they did not find any explosives and believe the threat did not pose any danger to the public.

Police officials have not provided details on the threats in Round Rock and Austin.

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Investigators believe that at least two of the threats originated overseas, said Nick Olivier, Round Rock police spokesman.

The Round Rock bomb threats did not lead to evacuating any businesses or offices, he said, though police did visit some of the locations where the threats were received.