Rousseff visited Lula, her political mentor, to express her solidarity, a day after his interrogation.

“I want to express my complete dissatisfaction with the fact that a former President, who regularly volunteered information to the authorities, has now been subject to a unnecessary detention to be interrogated,” she stated.

On Friday morning, Lula was detained at his apartment in Sao Bernardo do Campo and taken to Congonhas airport to answer accusations that he received embezzled funds from within the Petrobras corruption ring.

At a press conference on Friday after being interrogated by federal investigators for three hours, Lula said he felt “offended” but the support he had received inspired him to “keep fighting.” He said this was an attempt to besmirch his and Rousseff’s name.

Lula has said the investigators are running “a media circus”, not a serious probe.

Brazil’s Operation Lava Jato has so far led to the arrest of a wide range of politicians and businessmen suspected of illegally distributing funds from overinflated contracts signed with Petrobras.

Rousseff, meanwhile, urged that the Brazilian Constitution must be held sacrosanct while carrying out public investigations so that individual rights are not impinged upon.

“My government has guaranteed the autonomy of the public bodies responsible for investigating corruption. However, we have always asked them to respect the law and the rights of those under investigation,” she added.

For Rousseff, “it is necessary for investigations to continue until a punishment is finally meted out to those who should be punished. However, this must be done in a democratic and republican manner, by respecting the Constitution, and under the supervision of the Supreme Court, which are important safeguards.”

“Illegal leaks and judging someone before they have had their right to a defense do not help in finding the truth, they only serve to create intolerance and undemocratic rhetoric,” she noted.

Senior judges in Brazil voiced concern on Saturday over the detention of Lula.

Supreme Court Justice Marco Aurélio Mello told CBN Radio on Saturday that “nothing justified the use of force”.

Justice Gilmar Mendes termed the detention a “delicate situation” although he claimed the electoral funding of the Workers’ Party is questionable.

Rousseff and Lula waved to hundreds of supporters gathered outside the Lula residence on Saturday in a show of strength.

Rousseff and her Workers’ Party have repeatedly denied any wrongdoings.

Lula, a charismatic political operator who enjoyed a special bond with his countrymen, handpicked Rousseff to succeed him as the Workers’ party candidate in 2010 as he neared the end of his second four-year term.

In May last year, when the first complaints against him came out, Lula announced that the Brazilian elite feared the possibility of his return to power.