New lawsuit backed by Jay-Z, Yo Gotti slams 'barbaric' Mississippi prison conditions At least 18 inmates have died in Mississippi prisons since December.

For the second time in about a month, hip-hop artists Jay-Z and Yo Gotti are financially backing a federal lawsuit against the Mississippi prison system, bringing the number of inmates complaining of being subjected to "barbaric" conditions to 181.

The new lawsuit was filed on Wednesday in U.S. District Court in Greenville, Mississippi, on behalf of 152 inmates, most of them serving time at the state's largest and most notorious prison in Parchman.

Since late December, at least 19 inmates have died in Mississippi 's four state-run prisons, including seven killed in homicides and three by suicide, officials said.

Addressing conditions at the Parchman prison, the new lawsuit blames understaffing and poor funding for decades of problems.

"As a result, prisoners endure abhorrent conditions, abuse and constant violence, inadequate health care and mental health care, and overuse of isolation," the lawsuit states.

"The conditions of confinement at Parchman are so barbaric, the deprivation of health and mental health care so extreme, and the defects in security so severe, that the people confined at Parchman live a miserable and hopeless existence confronted daily by imminent risk of substantial harm in violation of their rights under the U.S. Constitution," the suit alleges.

Jay-Z's Roc Nation entertainment company and Yo Gotti also published a full-page ad in the New York Times directly addressed to Mississippi's new governor Tate Reeves, saying, "this is now part of your legacy."

"We need to be blunt: the alarming humanitarian crisis currently overwhelming Parchman Prison is spiraling out of control. We’ve heard you talk about bold and immediate action; now we need to see results before more lives are destroyed. The situation is critical," the ad reads.

It goes on to mention the nearly two dozen "senseless deaths" in the prisons since Dec. 29, and the "countless injuries and untold cases of mental and physical terrorism inflicted on inmates."

"Given those tragedies, if you don't act decisively, Parchman will soon be the site of a human catastrophe the likes of which the United States hasn't see in a generation," the ad reads. "If animals in the Jackson [Mississippi] Zoo were treated in such a way, you would immediately shutter it and launch an investigation."

Last month Jay-Z and Yo Gotti financially supported a similar lawsuit filed on behalf of 29 Mississippi prison inmates. The federal suit, filed on Jan. 16, alleges the prisoners' "lives are in peril" and claims that recent deaths were a "direct result of Mississippi’s utter disregard for the people it has incarcerated and their constitutional rights.”

In addition to the new lawsuit, Jay-Z's company released a YouTube video containing footage inmates took with contraband cell phones showing conditions in Parchman, including prison cells with no working toilets or running water, and other cells with leaking roofs. The video also showed a prisoner beating and chasing another prisoner through a cellblock with no guards in sight.

The video includes interviews with relatives of prisoners who have recently died in the penitentiaries, including the mother and sister of inmate A.D. "Buddy" Mills who, according to prison officials, died on Jan. 8 from natural causes at age of 42.

Mills' sister, Claudia Mills, said her brother suffered from diabetes and kidney failure. She said he died of renal failure.

"He was in Parchman 25 days, sick, we not knowing if he was getting his medicine or anything, not knowing if he was getting the proper care," Mills says in the video. "We know that he wasn't. We've been sent some videos [of] people crying out to help him."

Janice Sherman said in the video that her nephew, Joshua Norman, 26, was found dead hanging in his cell at Parchman on Jan. 26, four days after she assured him in a phone conversation that officials were working to improve conditions at the prison, which she described as "the scariest place on Earth."

"That was pretty devastating," she said of receiving the phone call that her nephew was dead. "It was my worst nightmare because it was never ... just never expected it. I knew there were struggles. I knew there were issues but I never lost hope of the possibility that he'd be OK."

Alarmed by a string of murders, suicides and cellblock riots, the Department of Justice announced on Feb. 6 that it was launching a civil rights investigation of the Mississippi prison system.

DOJ officials said the probe by the Civil Rights Division's Special Litigation Section is focusing on "whether the Mississippi Department of Corrections adequately protects prisoners from physical harm at the hands of other prisoners at the four prisons, as well as whether there is adequate suicide prevention, including adequate mental health care and appropriate use of isolation at Parchman."

Besides Parchman, the DOJ is investigating conditions at the South Mississippi Correctional Institution in Leakesville, Central Mississippi Correctional Facility in Pearl and the Wilkinson County Correctional Facility in Woodville.

The DOJ investigation was initiated about a month after 11 prisoner advocacy groups -- including the American Civil Liberty Union of Mississippi, the Southern Poverty Law Center and the Mississippi State Conference of the NAACP -- sent the agency a 23-page letter asking the federal government to investigate the state's prison system.

"Mississippi is deliberately and systematically subjecting people in its care to a substantial risk of serious harm due to understaffing, in violation of the rights secured and protected by the Eighth Amendment of the United States Constitution, and it is no exaggeration to say lives will be lost absent of immediate intervention," reads the letter, which was also signed by U.S. Rep. Bennie Thompson, D-Miss.

Mississippi's new governor, Tate Reeves, who took office on Jan. 14, has made fixing the prison system a major focus of his administration.

One of the first things Reeves did as governor was visit the troubled prisons and announce a series "common sense" changes, including a crackdown on contraband cellphones, which, he said, have been used to coordinate violence throughout the prison system. He's also started a process to weed out guards who are corrupt or have gang affiliations.

He immediately deployed maintenance teams to Parchman to improve conditions he called "terrible." In his first State of the State address, Reeves announced he had ordered the closing of the notorious Unit 29 at Parchman, where a deadly riot broke out in early January and thrust the crisis into the national spotlight.

ABC News' Ella Torres contributed to this report.