For the first time in three years, a new class of Cook County sheriff's police recruits is training for open slots, in a move that top officials hope will fill the department's depleted ranks.

The new class of 25 officers, which includes current courtroom deputies and jail guards, is part of a plan by Sheriff Tom Dart to fill about 50 police officer positions. They began their training Monday at Triton College in River Grove, sheriff's officials said.

The sheriff's office attributes the lower staff numbers to retirements and leaves of absence such as those away on military deployment.

The 25 officers will train alongside 23 cadets hoping to join several suburban departments.

In addition to patrolling the county's unincorporated areas and investigating crimes for both the sheriff's and forest preserve departments, sheriff's police also patrol south suburban Ford Heights, whose own police force folded in 2008.

Sheriff's police also lend their evidence technicians to police departments in 41 Chicago suburbs, officials said.