MENTOR, Ohio -- FBI officials said it they have strong leads into who is calling in bomb threats to stores across the country. Five threats were made in northeast Ohio Friday morning at three grocery stores and a Wal-Mart.

An FBI official said it appears the calls are coming from overseas, NewsChannel5's Bob Jones reported.

Threats received in northeast Ohio Friday morning were the latest in a series of threats made across the country this week.

The calls threatened that a bomb would explode in the stores unless money was wired to an account in Europe.

Agents said 24 businesses in 13 states have received the extortion calls and a couple of them wired between $10,000 and $12,000 to the scam artist.

The threats were phoned in around 6 a.m. to a Wal-Mart and Giant Eagle in Mentor and Giant Eagle stores in neighboring Mentor-on-the-Lake, Amherst and Green, authorities said.

The stores were evacuated, but police didn't find anything and they reopened within two or three hours.

"We believe these are all tied into the same individual or group of individuals that are doing this all over the United States," FBI special agent Scott Wilson said.

The FBI and police said Wednesday they were investigating bomb threats at more than 15 stores in at least 11 states.

The majority of the calls involve an extortion attempt and the threats appear to be coming from overseas, Wilson said.

"We have some strong investigative leads," he said.

Ohio colleges also have been receiving e-mailed bomb threats including Kenyon College in Gambier, Lorain Community College and the University of Akron, which received two. A suspect has been arrested in the second Akron threat.

For additional information go to www.fbi.gov.