SAO PAULO (Reuters) - Brazilian Supreme Court Justice Teori Zavascki, who was overseeing a graft investigation into scores of powerful politicians, was killed in a plane crash on Thursday, raising questions about who will take over the country’s biggest ever corruption case.

A Navy ship is seen near the wreckage from a plane, which crashed with Brazilian Supreme Court Justice Teori Zavascki, who was overseeing a graft investigation into scores of powerful politicians, in Paraty, Rio de Janeiro state, Brazil, January 20, 2017. REUTERS/Bruno Kelly

Rescuers found three bodies in the wreckage of the small, twin-prop plane that crashed off the coast of Rio de Janeiro state amid heavy rains, firefighters said. Federal prosecutors and police said they would immediately open an investigation in addition to that of aviation authorities.

Zavascki, 68, had in recent weeks been reviewing explosive testimony from executives at engineering group Odebrecht, expected to implicate an array of politicians in a vast kickback scandal centering on state-run oil company Petrobras and other enterprises.

The Hawker Beechcraft C90GT carrying Zavascki left a Sao Paulo airport around 1 p.m. (1500 GMT).

The plane crashed into the sea about 80 minutes later, roughly 3 km (2 miles) from the airport near the colonial tourist town of Paraty, according to air force and civil aviation authorities.

A witness to the accident, Lauro Koehler, who was on a boat near the site of the crash, told TV station GloboNews that visibility was near zero because of the rain, but that he saw the plane banking sharply and losing altitude on its approach.

“The curve the pilot was making seemed too severe,” Koehler said. “But the plane kept curving, to the point that my wife screamed, ‘It’s going to crash!’ Then the plane dropped into the sea.”

Koehler said the tip of the right wing clipped the water first and then its nose plunged into the ocean “with an incredible blow.”

The boat Koehler was on immediately went to the wreckage.

“We saw there was a woman alive inside the plane,” he said. “We tried to open the plane, but it was too late, and she sunk down into the wreckage.”

Luxury hotel chain Emiliano, which holds the license for the aircraft, confirmed the deaths of the pilot Osmar Rodrigues, whom family said had been flying for 20 years, and Carlos Alberto Fernandes Filgueiras, owner of the hotel chain, but gave no information about a fourth female passenger.

Condolences poured in from federal prosecutors and senior politicians, including some named in the sweeping graft probe - known as Operation Car Wash - that has shaken Brazil’s political establishment over the past three years.

Crusading anti-graft Judge Sergio Moro, who has spearheaded the graft investigation at the grassroots level for nearly three years, said in an emailed statement that he “was stunned” by Zavascki’s death, whom he called a “Brazilian hero.”

“Without him, there would be no Operation Car Wash,” Moro wrote. “I hope that his legacy, of serenity, seriousness and firmness in enforcing the law, regardless of the interests of those involved, even the powerful, will not be forgotten.”

RULING COALITION THREATENED

The investigation, involving at least 6.4 billion reais ($2.0 billion) in bribes for contracts with state-run enterprises, has led to the jailing of dozens of senior executives and has battered the ruling coalition of President Michel Temer.

Under Supreme Court rules, Zavascki’s case load would normally fall to the justice named by Temer to replace him, but an exception can be made for urgent matters, according to a court representative.

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Several of Temer’s ministers have fallen because of corruption allegations, and the president himself has been named by at least one Odebrecht executive in leaked plea bargain testimony.

Carlos Pereira, a professor of public administration at the Getulio Vargas Foundation in Rio de Janeiro and a leading expert on corruption, said Zavascki’s death was a serious blow but he was confident it would not derail the graft investigation.

“The death of Teori is unquestionably a stress test for Brazilian institutions, but there is no question that President Temer will be under tremendous pressure to nominate a replacement who has absolutely no hint of wanting to slow or halt the Car Wash investigation,” Pereira said.

Pereira said that close attention from judges, prosecutors, police and Brazilian civil society would safeguard the case.

“If there is any sign that anyone would use Teori’s death in an opportunistic manner to put up obstacles ... I have no doubt they will be severely punished by many sectors of society,” Pereira said.

The incident recalled the crash of another small aircraft in a storm along the same coastline that killed presidential candidate Eduardo Campos in the heat of the 2014 race. An investigation attributed that crash to pilot error.