AUSTIN, Texas — Investigators looking into the Texas youth prison system that has been upended by abuse and misconduct allegations arrested four current and former corrections officers Thursday on charges that include excessive force, theft and document tampering.

A fifth Texas Juvenile Justice Department employee is also wanted but remains at large, the Texas Department of Public Safety said in a statement, bringing the total number of juvenile correction workers facing criminal charges in the past year to at least nine. A 10th former correctional officer was convicted in July on charges of having sex with youth in custody.

The unfolding crisis is the second time Texas' juvenile corrections agency has been rocked by scandal. Lawmakers overhauled the system in 2007 and shuttered lockups after authorities believed at least 13 boys in custody had been sexually abused.

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A spate of new allegations is again raising fears. Among those arrested Thursday was Morsello Hooker, a 31-year-old corrections officer at a rural West Texas lockup. He's accused in court documents of picking up a 15-year-old who was lying on his back and slamming him on the ground.

The teenager said he was slammed down on his head and another correctional officer told investigators he saw Hooker use "a lot of force," according to court records. Hooker was released Thursday from Brown County Jail on $5,000 bond. It was not immediately clear if he had an attorney and a phone number listed to him was disconnected.

His arrest comes more than a month after Texas Gov. Greg Abbott ordered the Texas Rangers, the state's top criminal investigators, to delve into the state juvenile system that holds about 1,400 youth offenders in five lockups across the state.

In recent weeks, Abbott has also replaced the leader of the agency and an independent ombudsman, a position that was created in wake of the Texas juvenile lockup scandal a decade ago.

"Misconduct on the part of employees entrusted with the responsibility of protecting our youth will not be tolerated," Abbott said in a statement. "Today's announcement is one of many steps being taken to ensure that employees at the Texas Juvenile Justice Department are held accountable for their actions, and I am pleased with the progress being made."

Texas' juvenile system today is far smaller than it was at the height of the previous scandal, when the state had more than 5,000 offenders in lockups. But the department has long struggled with turnover and finding qualified correctional officers. Hooker had been on the job a decade before the alleged body slam that led to his arrest, according to agency spokeswoman Carolyn Beck, while the other three arrested Thursday had been on the job for less than three years.

They are Derrick Goodman, 56; Shannon Hoaglen, 41; and Derrick Day, 39. All worked at a North Texas lockup in Gainesville and were charged with official oppression. It was not immediately clear whether they had attorneys.