Search on for three escaped Indiana prisoners

(CNN) - Indiana authorities were searching Monday for two murderers and a rapist who apparently tunneled out of a maximum security prison in Michigan City.

Lance Battreal, Charles Smith and Mark Booher were discovered missing from their housing unit during a routine count Sunday, prison officials said.

"It appears they escaped by traveling in tunnels under the prison grounds," public information officer John Schrader said at a news briefing Sunday. "This is a very unusual occurrence."

Smith, 48, and Booher, 46, were serving time for murder, while Battreal, 45, was serving a rape sentence. All three had at least 30 years left on their sentences.

Residents should take precautions, Schrader said.

"There should obviously be concern because the individuals are, in fact, dangerous," he said.