A Chilean court ordered that a prominent former senator be placed under nighttime house arrest, while authorities investigate him for possible tax fraud and bribery.

Pablo Longueira, who was a presidential candidate in Chile's 2013 election, is accused by prosecutors of receiving close to $1 million from specialty mining company SQM from 2009 to 2013, then hiding the donations through falsified receipts in contravention of Chilean law. He also is accused of accepting bribes while working on a 2010 law that regulates mining concessions.

It also comes the day after Chile's public prosecutor said it was investigating a former high-level cabinet official in leftist President Michelle Bachelet's government for bribery and tax offenses.

Longueira has maintained his innocence.

"I understand the charges and I don't agree with them," he said during a brief appearance before a judge.

The current scandal caused Longueira to resign in March from the UDI party, which was founded by right-wing allies of former dictator Augusto Pinochet.

The UDI, like several other major political parties in Chile, has been wracked by a series of money-in-politics scandals in the past year and a half. That in turn has tarnished Chile's reputation for transparency and left Chileans disenchanted with politicians across the spectrum.