A bigamist accused of killing his second wife with the help of his first has been charged with murder months after the victim disappeared.

The body of Cecelia Bravo Cabrera has yet to be found, but investigators say they have evidence implicating Mexican couple Francisco Valdivia, 37, and Rosalina Lopez, 39.

Authorities claim Valdivia, of Visalia in central California, married Cabrera so he could get legal permission to remain in the US.

Francisco Valdivia (left) and wife Rosalina Lopez (right) have been accused of murdering Cecilia Bravo Cabrera, who has been missing since June

Valdivia and Lopez, who married in Mexico in 2007, were arrested on Tuesday. Cabrera has been missing since June 9, when she was seen leaving a casino with Valdivia. He had just finished a 90-day sentence for cultivating marijuana when he was arrested.

Police discovered a number of sites where Valdivia was growing marijuana while investigating his wife's disappearance.

The motive is unclear, but is said to be connected to the relationship between the two suspects, who arrived in the US illegally, and their victim.

Mother-of-four Cabrera, who was very active on social media until her disappearance, knew her marriage to Valdivia was a sham, but investigators believe he and Lopez threatened her if she ended the relationship, the Washington Post reports.

Sheriff Mike Boudreaux said: 'We do believe the motive surrounds this relationship of three people. It revolves around this relationship.'

But he said he was cautious about releasing information. Boudreaux stated: 'We have a great deal of information. But, detectives have put me on notice that any release of information may result in the integrity of this case.'

Sheriff's spokesman Teresa Douglass said authorities have evidence Valdivia and Lopez threatened Bravo and that detectives have 'significant digital forensic evidence' implicating the couple.

Cecilia Bravo Cabrera has been missing since June, and authorities believe she has been murdered

She declined to reveal what this information is.

Cabrera's car was set ablaze in an orchard and her children have not heard from her since her disappearance.

They are in protective custody, Douglass said. Boudreaux said they have been placed with close family members.

Valdivia was already in custody when he was arrested in connection with Bravo's death. He had been arrested on suspicion of cultivation of marijuana and jailed for lack of $1million bail.