MEXICO CITY (Reuters) - A former boss of Mexico's state oil company Petroleos Mexicanos facing corruption charges that could envelop leaders of the last government was taken to a hospital early on Friday shortly after his overnight extradition to Mexico from Spain.

Emilio Lozoya, wanted for alleged bribery and money laundering dating to his 2012-16 tenure in charge of the firm known as Pemex, entered the hospital soon after his arrival. The attorney general's office reported that a medical exam found that the 45-year-old had developed anemia and esophagus problems, and was in a generally "weak" state.

Lozoya, who landed in a plane at Mexico City airport shortly before 1 a.m. local time (0600 GMT), denies wrongdoing.

Once a rising star of Mexican politics, Lozoya has become a key witness in President Andres Manuel Lopez Obrador's drive to expose graft in and around the government he took over from his predecessor, Enrique Pena Nieto, in December 2018.

Lopez Obrador said Lozoya's trial would help shed light on and stigmatize acts of corruption in Mexico.

"It's really important so we can keep cleaning up corruption in the country, so these embarrassing acts are not repeated," the president told a regular news conference on Friday.

Under Mexican law, Lozoya must make an initial statement to a judge. Lopez Obrador said court proceedings would begin at midday. However, a government official told Reuters the hearing would now likely not take place on Friday.

On Friday morning, a convoy of SUVs took Lozoya from the airport to the Reclusorio Norte prison, Reuters images show.

Wearing a black face mask, baseball cap, and flak vest, Lozoya kept his head bowed in the back seat of one of the vehicles.

REVELATIONS

Scion of a political family and former luminary of the annual World Economic Forum in Davos, Lozoya has agreed to give information on alleged acts of corruption under the government of Pena Nieto, according to Lopez Obrador.

That prospect has fed expectations that Lozoya may make damaging revelations about ex-colleagues and politicians to reduce any possible sentence. Pena Nieto denies wrongdoing.

If the case were to lead to an investigation against the former president, Lopez Obrador said he would not stop it.

Prosecutors say Lozoya solicited and obtained funds from Brazilian firm Odebrecht for Pena Nieto's 2012 presidential campaign. Pena Nieto won, defeating Lopez Obrador.

In exchange, they contend, Lozoya awarded contracts to the firm as boss of Pemex and also took money for contracts from Mexican steelmaker Altos Hornos de Mexico.