(CNN) -- Dozens of businesses and institutions across the country received email threats Thursday afternoon, prompting evacuations and sweeps of buildings.
At this time it's unclear if the threats -- which have been received in San Francisco, New York, San Francisco, Seattle, Miami, Washington, DC, and other locations nationwide -- are connected. The FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives said they are aware of the threats and are working with law enforcement to provide assistance.
"As always, we encourage the public to remain vigilant and to promptly report suspicious activities which could represent a threat to public safety," the FBI said.
This email demanding $20,000 via Bitcoin was forwarded to CNN affiliate KOCO-TV in Oklahoma City by a viewer who received it at her business. It's unclear whether everyone who received a threat on Thursday received the same email.
The message was identical to an email warning posted on social media by the Cedar Rapids, Iowa Police Department and similar to descriptions of other threats posted on social media nationwide.
The Cedar Rapids Police Department posted: "The Police Department has found NO CREDIBLE EVIDENCE that these emails are authentic. It appears to be a robo-email that has been sent throughout the area hoping to scam businesses out of money. We have also received information that businesses in surrounding counties may have also received this email."
CNN is not disclosing the names of the sender and recipient or specifics of the Bitcoin account.
Threats at universities, media, courthouse
In Seattle, the University of Washington noted in a campus-wide alert that the FBI had "advised that the email is not a credible threat."
The university concluded sweeps of possibly affected buildings.
The Thurston County Courthouse in Olympia, Washington and the Park Record newspaper in Park City, Utah also received similarly threatening emails. People have been allowed back inside buildings at those locations, according to tweets on their verified Twitter accounts.
In California, the Riverside Sheriff's Office had "an influx of email threats" and is taking them seriously, although no threat has been substantiated.
The San Francisco Police Department responded to reports of bomb threats at locations throughout the city.
"We have received information that several other cities across the United States have received similar threats," police said.
Pennsylvania State Police are "investigating some bomb threats in the eastern part of the state," a spokesman for the department tells CNN.
"Penn State University Police, in conjunction with the Federal Bureau of Investigation, is investigating a message received by individuals in multiple locations on campus and across the state," the university said in a statement. "Police say this does not appear to be a legitimate threat, however, an investigation is ongoing."
University police later said the threat appears to be a hoax.
Email threats have also been received in Canada.
Vancouver Police Department Sgt. Jason Robillard tells CNN that businesses have received threats. He is not aware of any buildings that have evacuated.
The Chicago Police Department received 15 to 20 reports of emailed threats in the past few hours, according to Officer Jennifer Bryk.
Director of Communications Anthony Guglielmi tweeted, "#ChicagoPolice are working with federal partners on the investigation, and at this time there is no elevated threat level for the city of Chicago."
Threats were also emailed to the Charlotte News & Observer and the Raleigh News & Observer newspapers in North Carolina.
Dozens more threats continued to come in across the country later into the day, authorities reported.