When journalist Jesus Lemus was locked up in one of Mexico's most notorious prisons, next to killers and drug lords, he used the only writing material he could find to take notes: toilet paper.

Lemus was jailed in the maximum-security prison of Puente Grande in western Mexico in 2008 after a court convicted him of drug trafficking. Three years and five days later, he was acquitted and ready to write a book about his ordeal.

In his book, "The Damned: The Dark Story of an Extermination Prison," which will be presented in Mexico City next week, the 46-year-old journalist recalls how he spent most of the first six months naked in a tiny cell.

He also tells the stories of some of the penitentiary's most infamous inmates: Mario Aburto, convicted of the 1994 murders of a presidential candidate named Luis Donaldo Colosio; Alvaro Dario Valdez, alias "El Dubi," a member of a gang dubbed "Los Narcosatanicos"; and Daniel Arizmendi, a kidnapper nicknamed "The Ear Cutter" because he would slice off the ears of his victims.

In an interview with AFP, the journalist recalled how he used his toilet paper rations to scribble notes, which he would then fold up and hand to his wife, who hid them in her shoes to smuggle them out after conjugal visits.

At the time of his arrest in May 2008, Lemus was the director of El Tiempo, a newspaper in the town of La Piedad in the western state of Michoacan, where then president Felipe Calderon deployed soldiers in 2006 to root out drug cartels.

Lemus, who had been investigating links between cartels in Michoacan and the neighboring state of Guanajuato, said he was betrayed by one of his best sources, a police commander, who handed him to plainclothes officers.

"They handcuffed me, covered my face with a hood and kidnapped me for two days in a location unknown to police chiefs," Lemus told AFP.

"I endured torture that I never imagined could exist," he said.

He said his captors wrapped plastic bags around his head to deprive him of oxygen, electrocuted his testicles and beat him with wooden boards. Still, he refused to sign a confession saying he was a member of a drug cartel.

He later signed a document admitting he was detained alongside two drug traffickers, enough to get him sentenced to 20 years in prison.

In his first months in prison, he said guards would take him every night to a courtyard where they sprayed him with a water hose.

"They gave me beatings that I would rather not describe," Lemus said.

When two of his lawyers were murdered, Lemus had to take up his own appeal. Three years after his incarceration, a federal judge acquitted and freed the journalist in May 2011.

The media rights group Reporters Without Borders believes that Lemus is the only known case of a journalist jailed for drug trafficking under Calderon's 2006-2012 administration.

"We consider this an unprecedented case. We have not recorded any other case of a journalist detained for three years" and accused of links to drug trafficking," Reporters Without Border representative Balbina Flores told AFP.

Mexico has become one of the most dangerous places in the world for journalists, with at least 86 media people killed and another 18 missing since 2000.

Lemus, meanwhile, can no longer return to his former town, La Piedad, and struggles to find work in his field in the Michoacan state capital, Morelia.

His newspaper, once a critical voice against Calderon's administration, shut its doors after his arrest.