Police departments are investigating bomb threats sent Thursday afternoon via email to schools and businesses in Connecticut and across the country.

Connecticut State Police say they haven't found any of the threats to be credible but they encourage anyone who receives a suspicious email to immediately dial 911.

The emails have led to precautionary evacuations at schools in Griswold, Madison, Cromwell and Suffield, while threats also have been made to private businesses and public places in Newtown, Fairfield, Seymour and Wallingford.

About 1:10 p.m. Thursday, state troopers were dispatched to Griswold Elementary School after school administrators received a suspicious email, police said in a news release. The Emergency Services Unit and Bomb Squad also responded to the scene.

ESU members also were assisting local police departments in investigating similar incidents at the National Shooting Sports Foundation in Newtown and the Seybridge Plaza in Seymour. State police said its Cyber Crimes Investigative Unit and Connecticut Intelligence Center were working to identify the source of the emails.

Wallingford Police Lt. Cheryl Bradley said starting about 1:30 p.m., police heard of suspicious emails sent to several locations, including the Wallingford Public Library and Connecticut Food Bank.

She noted that the emails were generic and didn't name the businesses, but each indicated a bomb was planted and the sender was looking for money to be sent through Bitcoin, a cryptocurrency.

"We don't believe that they are credible, but we do respond — we continue to respond to every call that we get — and we're looking into the origins of the email," Bradley said.

The New York Police Department tweeted that an email is being circulated with a bomb threat asking for Bitcoin payment.

"At this time, it appears that these threats are meant to cause disruption and/or obtain money," it wrote. "We'll respond to each call regarding these emails to conduct a search but we wanted to share this information so the credibility of these threats can be assessed as likely NOT CREDIBLE."

Massachusetts State Police similarly said it's "tracking multiple bomb threats emailed to numerous businesses in the state."

Noting that the threats appear to be robo-emails to scam businesses out of money, the Cedar Rapids Police Department in Iowa posted the text of an email, which begins, "Hello. My man hid an explosive device (Hexogen) in the building where your business is conducted." The email said the "recruited person" will power the bomb if a cop is noticed, and requested $20,000.

In the wake of Thursday's emails, some schools across the country closed early and others were evacuated or placed on lockdown, The Associated Press reported. Authorities said a threat emailed to a school in Troy, Mo., about 55 miles northeast of St. Louis, was sent from Russia. The bomb threats also prompted evacuations at City Hall in Aurora, Ill., the offices of the News & Observer in Raleigh, N.C., a suburban Atlanta, Ga., courthouse and businesses in Detroit, AP reported. Other cities across the country to receive bomb threats include Chicago, Ill.; Orlando, Fla.; San Francisco, Calif., and Nashville, Tenn. 

The threats, which were written in a choppy style reminiscent of the Nigerian prince email scam, AP reported. Some of the emails had the subject line "Think Twice," and they were sent from a spoofed email address.

The FBI said it is assisting law enforcement agencies that are dealing with the threats. "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 in a statement.

Thursday's scare came less than two months after prominent Democratic officials and CNN's Manhattan offices were targeted with package bombs. The suspect in that case, Cesar Sayoc, is in jail while awaiting trial.

In 2015, an emailed bomb threat prompted different reactions from the nation's two largest public school systems. The Los Angeles school system closed down under threat of a mass attack, but New York City officials quickly saw it as a hoax.

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

Penn State University notified students via a text alert about threats to a half-dozen buildings and an airport on its main campus in State College, Pa. In an update, the school said the threat appeared to be part of a "national hoax."

Officials at Columbine High School in Colorado — where 12 students and a teacher were killed by two students in 1999 — were dealing Thursday with a bomb threat of a different sort, AP reported. Students were being kept inside for the rest of the school day after a caller claimed to have placed explosive devices in the school and to be hiding outside with a gun, the Jefferson County, Colo., Sheriff's Office said. Sheriff's spokesman Mike Taplin later said nothing was found at Columbine.

Two dozen other Colorado schools also temporarily were placed on lockout, meaning their doors were locked but classes continued normally, as the threat was investigated.

The Associated Press contributed to this report.

e.moser@theday.com