Police and prison guards aided by search dogs hunted Sunday for two convicted killers and a third man who escaped the maximum-security Indiana State Prison, apparently through underground tunnels and pipes.

All three men were considered dangerous, and prison officials used a telephone notification system to send alerts to nearby residents and others. It was not known if any of the men had weapons.

Authorities identified the men as Charles Smith, 48, and Mark Booher, 46, both of New Castle, and Lance Battreal, 45, of Rockport. Smith and Booher were convicted of murder in the 1990s. Battreal was serving time for rape. All three faced at least 30 more years behind bars.

Indiana State Police, federal marshals and local police and sheriff's deputies joined prison guards in searching for the three.

But authorities did not know where the men might be headed, Indiana Department of Correction spokesman Doug Garrison said. Investigators were poring over visitor logs and talking to the men's relatives in hopes of finding leads, Garrison said.

The men were discovered missing from their housing units around 10 a.m. Sunday, Garrison said. The prison said in a news release that it appeared they escaped by getting past the bars in the tunnels and pipe chases under the prison grounds. Garrison said it looked as if bars were removed.

The prison sits in a neighborhood on the outskirts of Michigan City, about 30 miles west of South Bend and not far from Lake Michigan and the Michigan state line.

Smith was sentenced in 1999 to 95 years for murder and had a projected release date in 2045. He has a tattoo of a scorpion on his right hand and a cross with dots on his left hand, the prison said.

Booher was sentenced in 1999 to 65 years for murder and 20 years for robbery. His projected release date was in 2041.

Battreal was sentenced in 1998 to 50 years for rape, 20 years for criminal confinement and three years for stalking. His projected release date was in 2047.

Additional details about their convictions were not immediately available from the Department of Correction.

Battreal and Smith may have both recently cut their hair or shaved it, the prison said.

New Castle and Rockport, the men's hometowns, are both more than 140 miles from the prison. New Castle is about 30 miles east of Indianapolis, and Rockport is about 30 miles east of Evansville.