Ohio authorities confiscated three fake handguns, drawings of handguns, and a fake explosive device at a maximum-security prison in what they're calling "a very serious and unique situation."

An investigation continues of the incident that unfolded Tuesday night at the Southern Ohio Correctional Facility in Lucasville, said prisons spokeswoman JoEllen Smith.

The first item found was a fake explosive device, located in a hole in a shower stall frame, and constructed of grout shavings, copper wire from ear buds, batteries, and a small radio, said Smith, spokeswoman for the Department of Rehabilitation and Correction.

The weapons, made to resemble Glock handguns, were made of bars of soap, pieces of eye glasses, battery casings, and carbon paper from legal kits provided to inmates, she said. Parts of a fourth gun were also found.

Events leading to the search began after an inmate called The Associated Press Tuesday afternoon, warning of a potential hostage-taking plot in the works.

The AP contacted the State Highway Patrol, which investigated along with prison authorities.

The inmates involved were placed in restrictive housing and the facility was back to normal Wednesday, said Smith.

"This was a very serious and unique situation," she said in an email. "We take very seriously any information that suggests there may be weapons within our facilities and immediate actions are taken to ensure the safety and security of the staff and inmates."

Prisoners with fake weapons can pose the same kind of threat as robbers who claim to have guns in their pockets, whether real or not, said Richard Lichten, a Los Angeles-based jail and police practices expert.

"It's no different in jail or prison," he said. "If somebody manufactures a weapon that's thought to be real, then that's an issue."

Compounding the problem are scattered examples of real weapons being smuggled into correctional facilities, said Lichten.

As a high-security prison, Lucasville holds many inmates who have racked up discipline problems in other facilities.

A 2016 legislative prison inspection committee found that Lucasville has traditionally had high assault statistics in part because of gang-affiliated prisoners.

An 11-day riot at the prison in 1993 was one of the country's longest and deadliest, leaving nine inmates and a guard dead by the time it ended.

Two former Lucasville inmates currently face charges in Scioto County for stabbing a guard 32 times last year near a prison infirmary.

One of those inmates has also been charged in a 2017 knife attack on four other inmates who were shackled to a table and unable to defend themselves.