Former President Ollanta Humala is being held in preventative detention at the same Peruvian prison where the ex-strongman he once tried to overthrow is serving a long sentence, authorities said Friday.

Humala and his wife were detained Thursday night after a judge ordered them held for up to 18 months while they are investigated on allegations of money laundering tied to undeclared campaign contributions from Venezuela and Brazilian construction giant Odebrecht. They have not been charged and they deny the accusations.

Humala, who left the presidency in 2016, was taken by helicopter Friday to the same prison in the capital that is holding former President Alberto Fujimori, who is serving a 25-year sentence for corruption. Humala led an unsuccessful army uprising against Fujimori in 2000 at the end of his decade-long rule.

A helicopter took Humala's wife, Nadine Heredia, to a female penitentiary where inmates include former Marxist guerrillas and major drug traffickers.

The case against the couple arose from testimony by the former head of the scandal-tainted Odebrecht in which he said he illegally contributed $3 million to Humala's 2011 presidential campaign.

The couple also is accused of taking undeclared funds from the late Venezuelan leader Hugo Chavez during a previous, unsuccessful presidential bid. Humala never declared the contributions and prosecutors contend he and his wife conspired to hide them for personal gain.

Authorities across Latin America have been moving to charge officials accused of taking some $800 million in bribes from Odebrecht. The company acknowledged the bribes when it signed a plea agreement in December with the U.S. Justice Department.

The bribes include some $29 million paid in Peru for projects built during the administrations of Toledo, Humala and former President Alan Garcia.

The same scandal has ensnared former Brazilian President Luiz Inacio Lula da Silva, who was convicted Wednesday and sentenced to almost 10 years in jail for taking gifts from another Brazilian builder that along with Odebrecht paid bribes to politicians in exchange for government contracts. Silva denies the accusation and will remain free while he appeals what he says are politically motivated charges.