IOWA CITY, Iowa —  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.

"The only thing I know for sure is they went over the wall in the southwest corner with a rope and a grappling hook they fashioned out of metal from somewhere," Fraise 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.

"I don't want to say I told you so, but those towers were put there for security, and when you don't man those towers, that puts a hole in your security," Fraise said.

State Rep. Lance Horbach, a Republican, criticized Fraise for suggesting budget cuts were a factor in the escape.

"In reality, we should explore why the taut wire system failed to alert guards and security staff that these two convicts were attempting to escape," 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.