Former WBC middleweight champion Julio Cesar Chavez Jr is being held in prison in his native Mexico reports say, weeks after he was deported from the United States.

The 39-year-old, who is the son of boxing icon Julio Cesar Chavez, was deported from California in July by Immigration and Customs Enforcement (ICE) agents just five days after he was defeated by decision by Jake Paul in what was his 63rd professional bout.

It emerged on Tuesday that the boxer has been detained in prison in Sonora in northern Mexico after authorities in the country alleged that he was involved with the Sinaloa cartel, which earlier this year was deemed a terrorist organisation by the United States.

It was reported that Chavez Jr was detained at a checkpoint in Nogales, close to the US border, on Tuesday before being transferred to a prison in Hermosillo, the capital of Sonora.

Mexico president Claudia Sheinbaum had previously stated that Chavez Jr was the subject of an arrest warrant amid allegations of arms trafficking and involvement in organised crime. A lawyer for Chavez Jr, as well as his family, have rejected claims that he is involved in crime.

Chavez Jr held the WBC middleweight title between 2011 and 2012, defending it three times — including against Ireland’s Andy Lee. However, after going undefeated in his first 48 professional fights, his success slowed after being defeated by Sergio Martinez for the world title in September 2012 — winning just eight his next 14 bouts.

His record also shows a loss to Anderson Silva, with his most recent win coming in July of last year against the MMA fighter Uriah Hall. In June, he was comprehensively outpointed through ten rounds by the influencer-turned-boxer Jake Paul.