A key witness in the corruption case of a former mayor of Peru’s capital, Lima, has been found dead at his home, Peruvian prosecutors say, less than three months before the trial is due to start.

José Miguel Castro, who was living under house arrest, was a municipality official during Susana Villarán’s term as mayor from 2011 to 2014.

He was a co-defendant in the trial with Ms Villarán, who is accused of receiving bribes worth $10m (£7.3m) from Brazilian construction firms.

In 2019, Ms Villarán admitted to receiving funds from these companies but denied that they were bribes. Mr Castro was collaborating with prosecutors on the investigation. The cause of his death is not yet known.

“He was the second most important person behind Ms Villarán,” prosecutor José Domingo Pérez told Peruvian news channel Canal N.

“We were expecting his valuable contribution” to the trial, he added.

Ms Villarán, 75, is accused of collusion, money laundering and forming a criminal organisation that received millions of dollars from construction companies Odebrecht – now called Novonor – and OAS.

Prosecutors said Mr Castro was the alleged criminal organisation’s second-in-command.

In 2019 Ms Villarán admitted taking funds from Odebrecht and OAS to finance her 2013 mayoral campaign to stay in office, but denied they constituted bribes.

The trial is due to start on 23 September.

Ms Villarán is one of a number of Peruvian politicians implicated in the Odebrecht scandal.

In 2016 the Brazilian construction giant admitted to bribing officials across Latin America and parts of Africa in order to obtain construction contracts.

A number of former Peruvian presidents have since been investigated, including Ollanta Humala, who was sentenced to 15 years in prison earlier this year, and Alejandro Toledo, who was sentenced to more than 20 years in prison last year.

Another former leader, Alan Garcia, killed himself as authorities arrived at his house to arrest him in 2019.

An investigation against another former president, Pedro Pablo Kuczynski, is ongoing. He denies the charges.