The men planted fake explosives, provided to them by an undercover FBI agent, under the Ohio Route 82 bridge in Sagamore Hills, which crosses Cuyahoga Valley National Park. The group was comprised of "self-proclaimed anarchists," who were participating in a May Day protest, according to the newspaper.
Those arrested by the FBI's Joint Terrorism Task Force were charged with conspiracy and attempted use of explosive materials, according to the Plain Dealer. The full FBI affidavit can be found here.
Other May Day protests took place across the United States Tuesday. According to the Seattle Times, city officials there warned the public about the possibility of violence amid a larger anti-capitalist protest being held. Occupy Wall Street in New York City also took up the May Day message, according to Bloomberg, calling for an international labor strike.