US federal officials in El Paso, Texas, have taken into custody Ismael "El Mayo" Zambada, the head of Mexico's Sinaloa cartel, one of the largest drug lords in the world.

Together with Joaquin "El Chapo" Guzman, who is incarcerated in the US, Zambada, 76, established the criminal organization.

Guzman's son, Joaquin Guzman Lopez, was also arrested on Thursday along with Zambada, according to the US Justice Department.

In February, Zambada was charged by US prosecutors with a conspiracy to make and distribute fentanyl, a drug more powerful than heroin that has been blamed for the US opioid crisis.

In a written statement on Thursday evening, US Attorney General Merrick Garland noted that the two men lead "one of the most violent and powerful drug trafficking organizations in the world".

"El Mayo and Guzman Lopez join a growing list of Sinaloa cartel leaders and associates who the Justice Department is holding accountable in the United States," Mr Garland said.

"Fentanyl is the deadliest drug threat our country has ever faced, and the Justice Department will not rest until every single cartel leader, member, and associate responsible for poisoning our communities is held accountable,” added Mr Garland, the top law enforcement officer in the US.

American prosecutors say the Sinaloa cartel is the biggest supplier of drugs to the US.

The US Drug Enforcement Administration (DEA) had been offering a reward of up to $15m (£12m) for Zambada's capture.

During Joaquin "El Chapo" Guzman’s trial in 2019, his lawyers accused Zambada of bribing the “entire” Mexican government in exchange for living openly without fear of prosecution.

"In truth he controlled nothing," Guzman’s lawyer, Jeffrey Lichtman, told jurors of his client. "Mayo Zambada did."

According to the US state department, Zambada is also the owner of several legitimate businesses in Mexico, including “a large milk company, a bus line, and a hotel”, as well as real estate assets.

Alongside fentanyl charges, he is also facing charges in the US ranging from drug trafficking, murder, kidnapping, money laundering and organised crime.

US authorities have previously noted that fentanyl is the leading cause of death for Americans aged 18 to 45.

In May, Zambada’s nephew - Eliseo Imperial Castro, who was known as "Cheyo Antrax" - was killed in an ambush in Mexico. He was also wanted by US authorities.

Zambada is arguably the biggest drug lord in the world and certainly the most influential in the Americas.

He had evaded authorities for decades, and as such, his arrest has come as a shock in Mexico.

Details of the arrests of the two men remain unclear, but it appears they flew into the United States.

As more information emerges, it will no doubt be heralded by President Joe Biden's administration as one of the most significant operations by the DEA in years.

Zambada co-founded the Sinaloa cartel in the wake of the collapse of the Guadalajara cartel at the end of the 1980s.

While Joaquin ‘El Chapo’ Guzman was the public face of the organisation and the most notorious of the two men, many believed it was in fact El Mayo who was its real leader.

Not only ruthless, he was also innovative, creating and maintaining some of the earliest links with Colombian cartels to flood the US with cocaine and heroin.

And more latterly, fentanyl.

His leadership of the criminal empire has endured in the face of changing presidents in Mexico and the US, amid repeated anti-drug offensives from successive governments and constant efforts by his enemies in other drug-trafficking organisations to bring him down.

That is no mean feat in the violent, dangerous and treacherous underworld in which he has operated as an unassailable kingpin for many years.

Yet that extraordinary resilience appears to have run out in El Paso, Texas – a city blighted by the influx of the synthetic opioid, fentanyl, much of which was smuggled in by his organisation.