DEER LODGE, Mont. -

Prison officials and Powell County law enforcement announced today they called off the ground search for 42 year-old Dean Randolph Jess.

Jess was serving time for raping a preteen girl back in 2004.

Warden Leroy Kirkegard explained they weren't getting anywhere with their on-foot search.

Kirkegard said, "it's very thick brush out there. Some of our staff were within 25 feet of each other when searching, and they couldn't even see each other."

They found the prison vehicle Jess is suspected of taking about one and a half miles south of the prison ranch Monday morning, and they say they have no idea where he could be now.

Kirkegard said, "the investigation is looking for everything in his cell. At this point there's nothing to point us to where he might be."

They said they've checked his record and they haven't found any clues that might have tipped them that he would take off.

"He was a very good worker," said Kirkegard, "kept to himself... no idea why this occurred."

The warden said the investigation will be handed over to the local police who will continue to follow leads.

Powell County Sheriff Scott Howard said, "there were officers out there beating the thick hard brush, we've backed that off but we're going to keep looking for him."

Kirkegard wanted to emphasize that the State Prison is a safe and secure facility, but says they might need to make some changes.

He said, "unfortunately when things like this happen it becomes a learning experience for us. We'll take a look at our policies and procedures and make sure mistakes don't happen again."

In April of 2011, Steven Dale Robb escaped from the prison ranch, and was on the run for more than a month before being arrested in Great Falls.

He is doing time for aggravated assault.

In June of 2007 inmates William Wilcut and Kelly Frank escaped, also through the prison ranch.

Frank made headlines in 2005 after being charged with plotting to kidnap David Letterman's son. Willcut was doing time for burglary.

Police captured them after five days.

One inmate remains at large after escaping prison grounds seventeen years ago.

Philip Sadowski murdered Robert Hare in Bozeman in 1989. He received 50 years in prison.

Sadowski worked on the prison ranch on a logging crew, living outside prison walls.

He used a prison work truck to make his escape, and hasn't been seen since.

The prison considers any escapee dangerous, you are urged to contact local law enforcement if you have any information on any escapee's whereabouts.