HANOI, Vietnam (AP) — Vietnamese police have widened their investigation into alleged graft and mismanagement connected to the state-owned oil and gas giant PetroVietnam that caused $69 million in losses.

Three PetroVietnam subsidiaries are being investigated for alleged abuse of power in appropriating $5.3 million, the Ministry of Public Security said in a statement late Wednesday.

The case centers on Ocean Bank, which was taken over by State Bank in 2015 at no cost after reporting losses of $445 million. PetroVietnam had owned 20 percent of the bank and lost all its investment after the takeover.

Ocean Bank's former chairman Ha Van Tham and general director Nguyen Xuan Son face embezzlement charges. They are among 51 bankers and businessmen including 46 senior executives at Ocean Bank who are standing trial in Hanoi for alleged mismanagement.

The bank gave $69 million in interest exceeding the rate set by the central bank to more than 50,000 individuals and nearly 400 companies and institutions including three subsidiaries of PetroVietnam, according to the accusations. Tham and Son are accused of initiating the policy and the other defendants are accused of implementing it.

The police statement said $3.4 million of the excessive interest was given to PetroVietnam Exploration and Production Corporation, $852,000 was given to Binh Son Oil Refinery company and $1 million was given to VietsovPetro, a joint venture between PetroVietnam and Russia.

Ocean Bank executives told the court they had to offer customers higher interest rates to attract savings and that the bank would collapse if they had not done so. They also told the court they had given senior executives of the three PetroVietnam's subsidiaries tens of thousands of dollars for their support. The senior executives denied the allegations.

Over the past two weeks, police have arrested or put under house four other former or current senior executives of PetroVietnam and a former deputy State Bank governor who oversaw bad debts at credit institutions for their roles in the case.

In May, Vietnam's ruling Communist Party fired Dinh La Thang as the party boss in the southern commercial hub of Ho Chi Minh City after finding he made "serious mistakes and violations" while heading PetroVietnam.

Thang had earlier been removed from the Politburo, the highest decision-making body of the Communist Party of Vietnam. He headed PetroVietnam from 2005 until 2011, when he was appointed transport minister. He served until early last year, when he took up the posts in the Politburo and Ho Chi Minh City.

The party's inspection committee said in April that Thang permitted an investment in the private Ocean Bank that exceeded regulations, causing "very serious losses to PetroVietnam."

"Currently, the Ministry of Public Security's Investigative Agency is focusing its forces to investigate, widen the criminal case and seriously handle those involved in accordance with the law and at the same time will have measures to retrieve properties to the state," the police statement said.

Vietnam ranks 113 out of 176 countries in the International Transparency's 2016 corruption index.

The Communist Party and government have stepped up their anti-corruption drive in recent years with courts sentencing several senior executives to death.