Detroit — Authorities are investigating a wave of emailed bomb threats to buildings Thursday in Metro Detroit and across the country that triggered evacuations, searches and workday disruptions.

Reports from buildings in downtown Detroit, Grosse Pointe Shores, Farmington Hills and Ann Arbor came about 2 p.m. Thursday, which triggered evacuations and searches, but authorities said there were no signs of explosives.

Authorities reported emails with the subject line: "Think Twice" sent from a spoofed email address. Samples of the email threats sent to The Detroit News by multiple sources describe a bomb being hidden in the building. According to the emails, the bomb would be detonated unless the targets made an online payment of $20,000 in Bitcoin.

New York City; Palm Beach, Florida; and Boise reported emailed threats. Aurora, Illinois, the offices of the News & Observer in Raleigh, North Carolina and a suburban Atlanta courthouse also received threats. Authorities said the scare appeared to be a hoax. The New York Police Department dismissed them as "likely not credible."

"Organizations nationwide, both public and private, have reported receiving emailed bomb threats today," said Shanon Banner, Michigan State Police spokeswoman. "They are not targeted toward any one specific sector."

Banner said there were no reports of explosive detonation relating to the threats. She said MSP is in "close communication with our federal partners."

The Guardian Building at 500 Griswold Street, 36th District Court and the Wayne County Treasury building at 400 Monroe all received the threats, police said. The buildings were evacuated at 2:05 p.m. Thursday.

The Wayne County Sheriff's Office also received the threat to "blow up" the Treasurer's building.

“One of our employees got an email threatening that if money wasn’t transferred into a designated account, they were going to blow up 400 Monroe,” said Pageant Atterberry, a Wayne County Sheriff’s spokeswoman. “Then, we got an anonymous phone call from someone threatening to blow up the same building."

The threats forced employees from their daily activities, and even a holiday celebration.

“We were having our holiday party, and they put on the loudspeaker to evacuate," said Gilda Crayton who works in the Guardian Building. "Then we heard the beep, beep, beep of the alarm.

“We had to take the stairs down. I work on the 33rd floor and my legs are like rubber right now.”

The Farmington Hills Police Department put out an alert, warning of several threats made to local businesses, calling them "part of an ongoing nationwide fraud."

Ann Arbor Police Sgt. Bill Clock said there were two bomb threats to an apartment complex and an office building in Ann Arbor. The Ann Arbor threats were at Sandalwood Circle, an apartment building on the city's north side and Victor's Way on the south side, Clock said.

Anyone with information about the emails can contact MSP's Michigan Intelligence Operations Center anytime at 1-855-MICHTIP (855-642-4847).

The Associated Press contributed to this report.

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