El Paso, Texas - Sinaloa Cartel co-founder Ismael Zambada Garcia appeared in a Texas courtroom in a wheelchair on Thursday to face US charges of drug trafficking, money laundering, and conspiracy to commit murder.

Zambada (76) was taken into US custody a week ago after landing in a private plane at an airstrip outside El Paso, Texas, with Joaquin Guzman Lopez, the son of the other Sinaloa co-founder, Joaquin "El Chapo" Guzman.

The alleged drug kingpin, also known as "El Mayo," appeared frail during a brief status hearing in his case in a federal court in El Paso, the El Paso Times reported.

Zambada attended the hearing in a wheelchair surrounded by four US marshals, the newspaper said, while another dozen marshals were stationed inside the courtroom and outside.

The hearing focused on whether one of Zambada's lawyers had a conflict of interest because he previously represented his son, who was arrested by the Mexican authorities in 2013 and extradited to the US.

Zambada, who has pleaded not guilty and is being held without bond, told US District Judge Kathleen Cardone he wanted to keep his attorneys, the El Paso Times said.

The second issue discussed at the hearing concerned whether Zambada should be put on trial with other indicted members of the Sinaloa Cartel. Zambada faces charges in multiple US states, and the Justice Department will ultimately decide where he is tried.

Cardone set the next status hearing for September 9.

There is ongoing mystery about the circumstances surrounding the arrests of Zambada and Guzman Lopez, whose father, "El Chapo," was convicted of drug charges in New York in 2019 and is serving a life sentence in a maximum security prison.

Initial media reports cited US officials as saying that Guzman Lopez had duped Zambada into boarding the plane by telling him that they were going to inspect property along the US-Mexico border.

But The New York Times, citing three federal law enforcement officials, said Zambada was ambushed in Sinaloa's state capital Culiacan at what he expected to be a "friendly meeting" with Guzman Lopez but instead witnessed a violent clash between bodyguards for the two men.

Zambada was reportedly handcuffed, had a bag put over his head, and was forced into a car. He was then flown across the border in a Beechcraft King Air plane to Texas, where he was taken into custody by US agents.

The 38-year-old Guzman Lopez, who faces drug trafficking, money laundering, and weapons charges, pleaded not guilty in a district court in Chicago on Tuesday and was remanded in custody.

He is one of the four sons of "El Chapo" known collectively as "Los Chapitos," or "The Little Chapos."

Zambada's lawyer, Frank Perez, has maintained that his client was "kidnapped" and taken to the US against his will.

The Times reported that the US government had no "real-time knowledge" of the specific methods that were used to bring Zambada across the border.

The Mexican government has also denied any advance knowledge of the operation.

The US State Department had offered a reward of $15 million for the arrest of Zambada and $5 million for the capture of Guzman Lopez.

US Drug Enforcement Administration chief Anne Milgram welcomed Zambada's arrest last week, saying it "strikes at the heart of the cartel that is responsible for the majority of drugs, including fentanyl and methamphetamine, killing Americans from coast to coast."