Drug lord Rafael Caro Quintero, who has been wanted for years, has been arrested in Mexico and is now to be extradited to the United States.

The 69-year-old was caught by marines in the northwestern state of Sinaloa, the Navy Ministry in Mexico City said on Friday (local time).

During the operation, 14 soldiers were killed when a helicopter crashed. 

Kidnapping, torture and murder of a special investigator

Caro Quintero aka "Rafa" was on the FBI's list of the ten most wanted criminals.

In 2018, the US federal police put a $20 million bounty on his head for information leading to his capture.

US authorities have accused the Guadalajara cartel co-founder of being responsible for the 1985 kidnapping, torture and murder of a DEA special investigator. 

US Ambassador to Mexico Ken Salazar said on Saturday that "no US personnel" were involved in Caro Quintero's arrest.

DEA boss Anne Milgram previously praised her agency's "team in Mexico" for "collaborating with Mexican authorities."

This was taken by some observers as an indication that US officials were involved.

Caro Quintero was arrested in the small town of Choix, Sinaloa, according to the Navy Ministry.

The ministry did not provide any information about the circumstances of his arrest.

The drug lord was then taken to the high-security prison at Altiplano near Mexico City.

Causes of helicopter crash unclear

There was initially uncertainty about the causes of the helicopter crash that killed 14 people.

Mexican President Andrés Manuel López Obrador confirmed via Twitter that the dead soldiers "supported those who were carrying out the arrest warrant".

The Navy Ministry had previously denied that the helicopter had crashed during the mission against Caro Quintero.

Mexico has used its army against drug traffickers since 2006. 

Caro Quintero had already served 28 years in Mexico for the murder of DEA agent Enrique Camarena.

He was caught in Costa Rica in 1985 and then sentenced to 40 years in prison.

However, due to a formal error in the verdict, he was released in 2013.

Although the Supreme Court later revoked the decision, Caro Quintero, dubbed the "drug lord of drug lords", had already gone into hiding.

Caro Quintero, once one of Mexico's most powerful drug lords, denied being responsible for Camarena's murder in an underground interview in 2016.

The Mexican-born DEA investigator had infiltrated the Guadalajara cartel.

His assassination severely strained US-Mexico relations.

It then took the anti-drug authorities of both countries decades to rebuild mutual trust. 

The Guadalajara cartel was particularly powerful in the 1980s.

It is considered a model for today's Mexican criminal organizations.

The cartel initially specialized in the production and export of marijuana, but later also entered the cocaine business.

Caro Quintero worked with Colombian drug lords in smuggling this drug from Colombia to the United States.

The fortune of Caro Quintero, who came from a poor background, was then estimated at half a billion dollars.

However, the murder of Camarena was followed by his descent.

The fight against the drug gangs intensified, leading to the dissolution of the Guadalajara cartel. 

However, this in turn fueled the rise of the Sinaloa Cartel led by Joaquín "El Chapo" Guzmán.

Guzmán was extradited from Mexico to the United States in 2017, where he is serving a life sentence.