A 20-year-old woman who made international headlines when she accepted the job as police chief in a violent Mexican border town has been fired for apparently abandoning her post after receiving death threats.

Marisol Valles Garcia was given permission to travel to the US last week for personal matters but failed to return to Praxedis G Guerrero as agreed, according to a statement from the city.

"In the absence of [her] presence on the agreed-upon day and since there was no notification of a need to extend the period of her absence, the mayor has decided to remove her from office," the statement read.

Local media have reported that Valles Garcia was seeking asylum in the US but there has been no confirmation. Her whereabouts are not known.

On Friday Chihuahua state human rights commission official Gustavo de la Rosa Hickerson said Valles Garcia's relatives and friends told him she had received telephone threats against her life the previous weekend.

A local official accompanied the police chief this week to the international bridge connecting El Porvenir to Fort Hancock, Texas, he said.

De la Rosa Hickerson and city officials tried to contact Valles Garcia by phone amid increasing speculation that she was seeking refuge but were unable to reach her.

Valles Garcia was named police chief of Praxedis G Guerrero in October. The town had been without a police chief since her predecessor was shot dead in July 2009.

Drug violence has transformed the town of about 8,500 people from a string of quiet farming communities into a lawless no man's land.

Two rival gangs – the Juarez and Sinaloa drug cartels – are battling over control of its single highway, a lucrative drug trafficking route along the Texas border.