Updated

Five federal agents arrested in connection with the videotaped torture and killing of drug hitmen have been released from prison for lack of evidence, the Mexico City government said Friday.

The release of the men, who were members of Mexico's elite Federal Agency of Investigation, raises further questions about the video shown on several Mexican television networks on Thursday and Friday.

The Mexico City government announced in a news release that the agents had left its Eastern Prison on Sept. 5.

"Of the eight people accused of being involved in the recently broadcast "narco-video," only three remain the Eastern Prison," it said.

The announcement contradicts a statement by Mexico's top drug prosecutor Jose Luis Santiago Vasconcelos, who said Thursday that the agents were "currently in the Eastern Prison."

Officials at the Federal Attorney General's Office refused to comment on the confusion and said Santiago Vasconcelos could not be located.

Excerpts of the DVD in question were first shown Thursday morning on the Web sites of the Dallas Morning News and Kitsap Sun, a newspaper in Bremerton, Wash.

The DVD shows grainy images of four men sitting bruised, bloody and bound before a curtain of black garbage bags. Prodded by an unseen interrogator, they describe themselves as hit men for the notorious Gulf Cartel, detailing how they kidnapped, tortured and killed their enemies.

They also say they worked with Mexican law enforcement agencies.

In one section of the video, according to the Dallas Morning News, a hand clutching a gun appears and shoots one of the men in the head.

Following the release of the DVD, Santiago Vasconcelos gave a news conference, in which he said the film was made by a rival drug cartel and aimed to smear the Mexican government with false accusations.

He said the cartel hired 11 federal agents to kidnap and torture those filmed. Eight of these agents had been arrested and three were on the run, he said.

He said the DVD was likely to spark a new wave of violence among traffickers looking to settle personal scores.

This year there has been a wave of bloodshed as the Gulf and Sinaloa Cartels fight for billion-dollar drug smuggling routes to the United States.

Since Jan. 1, more than 1,000 people have been slain in drug-related killings across Mexico.

The alleged hit men appearing on the video admit to carrying out some of these killings, including the slaying of radio reporter Dolores Garcia Escamilla, who was shot outside her office in April. The attacker has never been identified.

Along with such crimes, the men discuss what they describe as the planned killing of Alejandro Dominguez, according to the Morning News. Dominguez was gunned down in June, 8 hours after becoming the Nuevo Laredo police chief.

Dominguez's killing prompted President Vicente Fox to send more federal troops and agents to the city, which is on the front line of Mexican drug cartels' battle for territory.

The DVD, time-stamped May 16, was sent anonymously to the Kitsap Sun last month. That newspaper forwarded it to the Morning News.