WASHINGTON, Jan. 24 - The American Civil Liberties Union released documents on Monday describing complaints of serious abuse of Iraqi civilians, including reports of electric shocks and forced sodomy, and accused the military of not thoroughly investigating the cases.

The documents list dozens of allegations of abuse at American detention centers - the use of cigarettes to burn prisoners, aggressive dogs, electric shocks, sexual humiliation and beatings - that began at about the same time such acts were occurring at Abu Ghraib prison.

But it is not always clear whether every case described is a new incident; many details, including the names of victims and of the accused, were blacked out before the documents were provided to the A.C.L.U. as part of its litigation.

Jameel Jaffer, a lawyer for the organization, said gaps in the files made it difficult to draw any definite conclusions about a particular case. "But overall there does seem to be a clear pattern here, and that is that it is difficult to say the government was aggressive in investigating these allegations of abuse," he said.

Lt. Col. Pamela Hart, an Army spokeswoman, declined to discuss any particular case mentioned in the documents. But she said, "The Army has aggressively investigated all credible allegations of detainee abuse and we've held soldiers accountable for their actions."

The documents list several sites where abuses are reported to have taken place, many of them at the detention center at Adhamiya Palace, one of Saddam Hussein's villas in Baghdad. The documents contain allegations from detainees about being abused and statements from American contractors who said they saw the effects of beatings.

In one case, a detainee said that while at Adhamiya Palace, his nose was pinched while water was poured down his throat, a wooden stick was inserted forcefully into his anus and electric shock was applied to his genitals. Some of the allegations were directed against Iraqi policemen. One contractor who said he was assigned to screen detainees brought to Abu Ghraib said that many who had come from Adhamiya arrived with serious injuries, including one boy with a bleeding rectum. He said the boy had told him that an Iraqi policeman had sodomized him with a soda bottle and that American soldiers were present.

Most of the previously undisclosed allegations concern the early months of last year, while some are said to have occurred as recently as July. The more than 4,000 pages of documents were released by the Army in response to a lawsuit brought by the American Civil Liberties Union and other groups that have accused American forces of serious abuse, even torture, in treating detainees.

The new documents show that some allegations of assault were investigated and soldiers were disciplined. Mr. Jaffer, of the A.C.L.U., said that in the more than 50 cases mentioned, military investigators had ruled in all but a few that there was insufficient evidence to proceed.

The new accusations generally concern the behavior of American Special Forces, as opposed to prison guards or interrogators, who have been accused at Abu Ghraib.

The files released on Monday concerned only cases that had been resolved by military investigators; there may be other cases still under investigation.

Colonel Hart said that more than 300 criminal investigators had looked into accusations of mistreatment of detainees and that more than 100 military members had been disciplined. "The Army's record of investigating detainee abuse continues to be thorough and fair," she said.