WASHINGTON (CNN) -- The Justice Department filed suit Thursday against the state of Mississippi for failing to end what federal officials call "disturbing" abuse of juveniles and "unconscionable" conditions at two state-run facilities.

In announcing the suit, top department civil rights officials cited shocking practices including the hog-tying of children, and allegations that youths were forced to eat their own vomit.

"Our investigation found evidence that juveniles were routinely hit, shoved and slapped by staff, that juveniles were sprayed with pepper spray while in restraints," said Assistant Attorney General for Civil Rights Alex Acosta.

"In some cases suicidal girls were stripped naked and isolated for extended time periods in windowless empty 'dark rooms' with only a drain in the cement floor to serve as a toilet."

"We found evidence of systemic abuses including hog-tying and pole-shackling. It was even reported that girls, overcome by the heat during drills, were forced to eat their own vomit," he said.

Mississippi officials said they have been working to correct problems at the facilities.

The two state-run facilities investigated are the Oakley Training School in Raymond and the Columbia Training School in Columbia, which together house about 600 juveniles.

Oakley houses 325 boys ranging in age from 10 to 18 years old, and Columbia holds approximately 100 boys ages 10 to 15, as well as 100 girls ages 10 to 18, according to the Justice Department.

"The conditions at Oakley and Columbia are unconscionable," Acosta said. "This is no way to set juvenile offenders on the course to law-abiding and productive lives."

After the announcement, Mississippi officials criticized the Justice Department, saying federal prosecutors should have entered into a private settlement agreement with the state, instead of filing the suit.

"We should be spending our time and our money protecting our children instead of wasting it on unnecessary litigation and legal fees," said state Attorney General Michael Moore, in a written statement.

Moore spokesman Jonathan Compretta said the state has worked since June to fix all abusive programs, conduct and procedures.

Acosta and other top civil rights officials said they decided to take Mississippi to court because talks had failed to end the abuses, which the government first outlined to Mississippi in a 48-page report in June.

"Mississippi officials have taken some important first steps toward reform," Acosta told reporters at a Justice Department press conference in Washington. But he added, "Despite some initial progress, we have been unable to obtain agreement on an in-court settlement."

"We have information this is still going on," said a Justice Department lawyer with the special litigation section, which conducted the investigation.

The Oakley Training School is one of the facilities named in the investigation. The Justice Department is demanding Mississippi immediately establish procedures, rules, and additional checks to ensure the civil rights of the juveniles are not violated.

Officials said civil rights abuses stemming from racial or gender bias tend to receive extensive publicity, but the civil rights of institutionalized individuals rarely gain wide attention because there are few advocates for them.

Although the conditions at the Mississippi institutions are among the worst civil rights attorneys have found, similar facilities in many other states are troubled, the officials said.

In the past two years the Justice Department has opened 33 investigations into the conditions of confinement at nursing homes, mental health facilities and institutions for persons with developmental disabilities.

Current investigations into juvenile justice facilities involve federal probes in Arizona, California, Maryland, Michigan, Nevada and South Dakota, officials said.