The number of people who have been reported missing in the violence-wracked Mexican state of Sinaloa has doubled since two rival factions of a drugs cartel started a bloody battle for control of their criminal organisation.

According to official figures, more than 200 people have disappeared since the two factions of the Sinaloa cartel declared war on each other almost three months ago.

The feud broke out after the arrest in the US of Ismael "El Mayo" Zambada.

His followers, known as "Los Mayos" or "La Mayiza", say he was betrayed by the son of the infamous founder of the Sinaloa cartel, Joaquín "El Chapo" Guzmán, and have turned on members of his faction, known as "Los Chapitos".

Mexican President Claudia Sheinbaum has despatched her security chief, Omar García Harfuch, to Sinaloa state to quell the violence.

The spike in murders and disappearances in Sinaloa has overshadowed Sheinbaum's first months in office.

She was sworn in as Mexico's first female head of state on 1 October after a campaign in which she had promised to maintain the approach taken by her predecessor in office, who avoided direct confrontations with the cartels.

"There will be no return to the irresponsible drug war," she had said in her inaugural speech, ruling out a more militaristic approach.

But faced with growing criticism in her own country and pressure from US President-elect Donald Trump, who wants Mexico to do more to curb the trafficking to the US of the synthetic opioid fentanyl, Sheinbaum on Wednesday appeared to make tackling the violence in Sinaloa her priority.

In a news conference, she said her Administration would take a "zero tolerance" approach.

She also praised the security forces for making Mexico's biggest fentanyl bust to date.

"This is an investigation that has been going on for a long time and yesterday, it gave these results. It is the largest seizure of fentanyl pills ever made," she said.

Earlier, Mexico's top security official, Omar García Harfuch, had announced on X, formerly known as Twitter, that the fentanyl pills seized at two properties in Sinaloa were worth $394m (£309m) and weighed more than a tonne.

"These actions will continue until the violence diminishes in the state of Sinaloa," he said in the post [in Spanish].

News of the massive fentanyl bust came just over a week after Trump threatened to impose 25% tariffs on goods coming from Mexico and Canada on day one of his presidency.

He said the tariffs would remain in place until "until such time as drugs, in particular fentanyl, and all illegal aliens stop this invasion of our country".

Mexican officials also announced on Wednesday that they had detained more than 5,200 migrants across the country the previous day, in what appeared to be a response to President Sheinbaum's promise to Trump to stop a migrant caravan moving north through Mexico from reaching the US border.