MEXICO CITY – A nephew of Ismael “El Mayo” Zambada, a top Sinaloa drug cartel leader, committed suicide at a government safe house, the Mexican Attorney General’s Office said.

Jesus Zambada Reyes was a “cooperating witness” since his arrest last year, the AG’s office said.

Zambada Reyes was arrested in October 2008 along with his father, Jesus “El Rey” Zambada, considered one of the top leaders of the Pacific drug cartel, the AG’s office said.

Mexican officials sometimes refer to the Sinaloa drug cartel, which is led by drug lord Joaquin “El Chapo” (Shorty) Guzman, as the Pacific cartel.

Zambada Reyes hanged himself at a Mexico City residence that belongs to the AG’s office.

Officials did not say whether the 22-year-old Zambada Reyes was under police guard at the time of his death or whether he was still working with the SIEDO organized crime unit of the AG’s office.

“From the beginning, all the information has indicated that his death occurred by suicide ... hanged from a rope tied to his neck,” the AG’s office said, adding that the autopsy established the cause of death as “asphyxiation by hanging.”

Investigators found no evidence to indicate that Zambada Reyes “struggled or fought with third persons” prior to his death, the AG’s office said.

“Indications are that he previously communicated to other people his desire to take his life,” the AG’s office said, adding that the investigation was continuing.

Zambada Reyes’s uncle, Ismael, is one of the most-wanted drug traffickers in Mexico.

Mexico’s most powerful drug trafficking organizations, according to experts, are the Tijuana cartel, which is run by the Arellano Felix family, and the Gulf, Juarez and Sinaloa cartels.

Two other large drug trafficking organizations, the Colima and Milenio cartels, also operate in the country.

“Los Zetas,” a group of army special forces veterans and deserters who initially worked as hitmen for the Gulf organization, may now be operating as a cartel, some experts say.

La Familia Michoacana, which operates in the western state of Michoacan, the southern state of Guerrero and the central state of Mexico, which surrounds the Federal District and forms part of the Mexico City metropolitan area, is considered the largest trafficker of synthetic drugs in Mexico.

The Sinaloa organization is the oldest cartel in Mexico and is led by Guzman, who was arrested in Guatemala in 1993 and pulled off a Hollywood-style jailbreak when he escaped from the Puente Grande maximum-security prison in the western state of Jalisco on Jan. 19, 2001.

Guzman, considered extremely violent, is one of the most-wanted criminals in Mexico and the United States, where the Drug Enforcement Administration has offered a reward of $5 million for him.

El Chapo made the Forbes list of wealthiest people in the world this year, ranking 700th with an estimated fortune of $1 billion.