Iraq's interior minister said Tuesday more than 40 police officers face charges after an investigation into prison abuse found inmates incarcerated without warrants and others with their rights violated.

Jawad al-Bolani's announcement came as the government tried to contain a scandal over charges of widespread torture in Iraqi prisons, which is threatening to become a major issue ahead of Jan. 30 national elections.

He spoke during a tour of one of the most notorious prisons in eastern Baghdad, where prisoners were packed by the dozens into small cells with clothes hung on the wall to dry and pillows on the floor.

Politicians loyal to Shiite cleric Muqtada al-Sadr — whose followers were rounded up in droves last year as part of a crackdown against militia fighters — kept up their pressure on the government over prison conditions.

Sadrist lawmaker Ali al-Miyali told reporters Tuesday that torture has been used to extract confessions in a prison in the southern city of Diwaniyah and other facilities.

He also alleged that inmates have been detained on false accusations from politically motivated informants and some families have been forced to bribe "corrupt police officers" for the release of their relatives or even for visitation rights.

"We demand that the government punish those officers and eliminate them from the security services," he said.

More than 300 detainees from al-Sadr's movement began a hunger strike this weekend at the Rusafa prison in eastern Baghdad, hoping to draw attention to their plight, according to family members and aides to the cleric.

The issue took on added prominence last week when a Sunni lawmaker who was an outspoken advocate of rights for prisoners from both Islamic sects was killed after delivering a sermon at a Baghdad mosque.

Harith al-Obeidi, the head of the Sunni Iraqi Accordance Front, was slain Friday after delivering a sermon that raised the complaints of prisoner abuse. He also was involved in a parliamentary debate on the issue.

The interior minister said a special committee had looked into 112 complaints following a June 11 parliamentary session on the issue, al-Bolani said.

The committee found 23 cases of human rights abuses and 20 cases of inmates incarcerated without warrants, leading to court action against 43 police officers, he said, adding that dozens of others were being questioned for allegations that have surfaced recently in the media.

Concern about abuse within the Iraqi judicial system has have been heightened as the United States has begun to turn over control to the Iraqis of thousands of detainees in its custody under a new security pact that would end the U.S. mission in Iraq by 2012.

The United Nations has warned of overcrowding and "grave human rights violations" of detainees in Iraqi custody and called for thorough investigations of reports of mistreatment and torture.

The U.S. military has been heavily criticized for its past treatment of detainees, particularly following the publication of photos of inmates being humiliated by American guards at the former Abu Ghraib prison.

American authorities implemented a series of reforms following the revelations and they are no longer able to hold suspects without charge as they have done since the U.S.-led 2003 invasion due to a security pact that took effect on Jan. 1.

In line with the agreement, the number of Iraqi detainees in U.S. custody has dropped to 10,956 from a peak of 26,000 in 2007, the military said Tuesday, adding it has transferred nearly 700 inmates to Iraqi facilities and released 3,682 so far this year.

It said the U.S. detention center in southern Iraq known as Camp Bucca was expected to close in mid-September, while the prison at the U.S. base in Taji is due to be turned over to the Iraqi government early next year.

Camp Cropper, the prison on the outskirts of Baghdad where Saddam Hussein was held before he was executed, will be the last U.S. detention facility to be turned over to the Iraqis, currently scheduled for August 2010, according to a military statement.

In other developments Tuesday, a roadside bomb killed a U.S. soldier near the southern city of Samawah, raising to at least 4,314 the number of U.S. military members who have died in Iraq since the war started.

A commuter bus traveling from Baghdad to the southern city of Basra also caught fire, killing 14 passengers on board, Iraqi officials said. Police said the fire broke out in the engine at the rear, then wind caused the flames to fan through the rest of the bus.