Her husband, Senator Rafael Moreno Valle, and two pilots were also killed. Reports say there was a third passenger on board, who also died.

Monday's accident happened shortly after the aircraft took off from the state capital of Puebla.

Ms Alonso became Puebla's first female governor after hotly contested polls.

The 45-year-old was a member of the centre-right PAN party.

The deaths of the governor and her husband were confirmed by Mexico's new President, Andrés Manuel López Obrador.

In a tweet (in Spanish), President López Obrador expressed "deepest condolences" to the relatives of the two politicians.

He said an investigation would be launched to establish "the truth" about what caused the crash.

Mexican officials later said they believed the helicopter went down after suffering an unspecified failure near Puebla, Mexico's second largest city.

Ms Alonso had taken office on 14 December, narrowly beating in July's elections Manuel Barbosa, President López Obrador's favoured candidate for the governorship of one of Mexico's most populous states.

President López Obrador's Morena party had alleged widespread irregularities and fraud in the poll, and the final results had to be validated by an electoral tribunal.

Mr Barbosa said the deaths of Ms Alonso and Mr Moreno Valle was a "tragedy that no-one wishes to anyone".

"I am shocked and in mourning. My sympathies to their loved ones. This is not the time to make any speculation," Mr Barbosa added.

Mr Moreno Valle also served as Puebla's governor between 2011 and 2017.

Puebla's parliament will now have to appoint an interim governor until new elections are held.

Monday's accident comes after a number of high-profile deaths in helicopter crashes over the years in Mexico, including Interior Minister Francisco Blake Mora in 2011, the BBC's Will Grant reports.

Earlier this year, 13 people died when a minister's helicopter crashed into a crowd, although the minister himself survived, our correspondent says.

More about: Mexico