Dozens of emaciated men with sunken cheeks and protruding ribs lie silently in an infirmary at Haiti's largest prison, most too weak to stand. The corpse of an inmate who died miserably of malnutrition is shrouded beneath a plastic tarp.

Elsewhere, prisoners are crammed shoulder-to-shoulder in cellblocks so overcrowded they have to sleep in makeshift hammocks suspended from the ceiling or squeeze four to a bunk. New arrivals at Haiti's National Penitentiary jostle for space on filthy floors where inmates on lockdown 22 hours a day are forced to defecate into plastic bags in the absence of latrines.

"Straight up: This is hell. Getting locked up in Haiti will drive you crazy if it doesn't kill you first," said Vangeliste Bazile, a homicide suspect who is among the about 80 percent of those incarcerated who have not been convicted of a crime but are held in prolonged pretrial detention waiting for their chance to see a judge.

Overcrowding, malnutrition and infectious diseases that flourish in jammed quarters have led to an upsurge of inmate deaths, including 21 at the Port-au-Prince penitentiary just last month. Those who monitor the country's lockups are sounding an alarm about collapsing conditions.

"This is the worst rate of preventable deaths that I have encountered anywhere in the world," said Dr. John May, a Florida physician who co-founded the nonprofit group Health Through Walls to improve health conditions in the Caribbean and several African nations.

Prisoners at the crumbling Port-au-Prince penitentiary flocked around a team of Associated Press journalists on a recent morning, eager to discuss their cases and complain of being all but forgotten at the foul-smelling furnace. Some 40 percent of the country's 11,000 inmates are housed there in appalling squalor, a block away from government headquarters, and many are tormented by the prospect of indefinite detention.

"I'm really scared I won't get to see a judge until I'm an old man," said Paul Stenlove, a 21-year-old murder suspect who was put in the prison 11 months ago.

Prisons are crowded, dismal places in any number of countries. But Haiti's penal system is by far the globe's most congested, with a staggering 454 percent occupancy level, according to the most recent ranking by the University of London's Institute for Criminal Policy Research. The Philippines comes second with 316 percent occupancy.

Inmates, some waiting up to eight years to see a judge, try to keep their sanity by maintaining a daily routine of push-ups and lifting jugs filled with dirty water. Others play checkers or dominoes. Sentenced convicts and the far greater numbers of untried suspects pool together what little money they can scare up to buy small TVs and radios for their shared cells.

But with widespread malnutrition and rats scampering through cells made for 20 men but now crammed with 80 to 100 it's hard to focus on anything but basic survival.

"Only the strong can make it in here," said Ronel Michel, a prisoner in one of the crumbling cellblocks where exterior walls are stained with dried feces because the men have to drop their excrement out of barred windows.

Not all the inmates are weakened by hunger. Some are provided meals by visiting relatives and others are permitted by guards to meet with contacts to bring in food, cigarettes and other things. AP reporters saw one inmate with a wad of cash standing near the main gate ordering spaghetti and fried plantains from a vendor outside.

But the large majority of prisoners are dependent on authorities to feed them twice a day and get little more than rationed supplies of rice, oats or cornmeal. Even clean drinking water is often in short supply.

Prison authorities say they try their best to meet inmates' needs, but repeatedly receive insufficient funds from the state to buy food and cooking fuel, leading to deadly cases of malnutrition-related ailments such as beriberi and anemia.

"Whenever the money is late it's the prisoners who pay," said National Penitentiary Director Ysarac Synal.

Haiti's penal system is so overcrowded that suspects are held indefinitely in other fetid, cramped pens, including cells at four police stations, where malnutrition is common. Three inmates recently died of malnutrition ailments at a prison in the southern city of Les Cayes.

Life was supposed to be getting a little better for prisoners here. In 2008, the Inter-American Court of Human Rights ordered Haiti to bring its "inhuman" prisons in line with minimum international standards. After a devastating earthquake in 2010, donor nations and humanitarian organizations launched projects aimed at building new infrastructure and improving deplorable conditions.

One of these improvements was the "Titanic" cellblock at the National Penitentiary, built with $260,000 from the International Committee of the Red Cross. Its cement tower was intended to ease overcrowding. But a few years after opening, it is possibly the most crowded block in the prison.

"It's a permanent struggle just to keep them (Haitian prisoners) alive," said Thomas Ess, chief of delegation for Haiti's Red Cross office.

Severe overcrowding is partly due to rampant corruption, as judges, prosecutors and lawyers join in creating a market for bribes, said Brian Concannon, director of the nonprofit Institute for Justice and Democracy in Haiti.

"If nine in 10 prisoners is in pretrial detention, and a person has no prospect of getting a fair trial for years, his family will find some way of raising the funds to bribe him out, regardless of guilt," Concannon said.

Some foreign officials who have seen the system up close are exasperated by a lack of political will to solve problems of corruption, sluggish justice and prison conditions.

"It is unconscionable that despite hundreds of millions of dollars in international aid the situation is even worse today, with inmates suffering from severe malnutrition and dying of preventable diseases," U.S. Sen. Patrick Leahy, who toured the National Penitentiary in 2012, said in an email.

As men continue to die unnecessarily at the National Penitentiary, Port-au-Prince chief prosecutor Danton Leger has been holding mass burials for prisoners, purchasing caskets and flower arrangements. Dead inmates, regardless of whether they were convicted or not, were previously dumped in a potter's field.

"The men in there are forced to live like animals. They can at least be buried like people," Leger told AP.