Authorities searched on Tuesday for two convicted murderers who escaped from the Iowa State Penitentiary by using a homemade grappling hook to scale an unguarded section of the prison’s limestone walls.

Martin Shane Moon, 34, and Robert Joseph Legendre, 27, broke out Monday night from the prison in Fort Madison, where they were serving life sentences.

State Sen. Gene Fraise said he was told by prison officials that the inmates somehow got around a wire that is supposed to activate an alarm when touched. The wall also had razor wire, he said.

Fred Scaletta, a Corrections Department spokesman, said the inmates used upholstery webbing, a material used by inmates who made furniture at a shop inside the prison, to scale the wall. The guard tower in that section of the prison was unmanned at the time because of budget cuts, he said.

Authorities said the escaped convicts may have stolen a car from a home a mile and a half from the prison and close to a bridge over the Mississippi River into Illinois.