Former police Lieut. Gen Phan Huu Tuan, former deputy head of the general department of the intelligence service, is accused of intentionally revealing state secrets.
Vietnamese President Tran Dai Quang on Tuesday stripped Tuan of his "people's police" title, the Ministry of Public Security said.
Four other former or current Danang officials, including Minh's successor Van Huu Chien, were placed under house arrest while an arrest warrant was issued for another ex-police officer who worked under the Ministry of Public Security.
The suspects have alleged connections to real estate developer Phan Van Anh Vu, a former senior intelligence officer who was arrested in January after being deported from Singapore after using a false identity to enter the city state.
The 42-year-old Vu was initially investigated for revealing state secrets, but now police have also included tax evasion and abuse of power.
Police are investigating nearly three dozen properties related to Vu.
The properties had previously belonged to the state and were reportedly sold to Vu at below market price. Vietnam has stepped up its fight against corruption in recent months with the state energy giant PetroVietnam and the banking sector at the center.
Scores of former or current senior executives of PetroVietnam and bankers have been put on trial. The most senior official to fall in the crackdown was Dinh La Thang, former member of the all-powerful Politburo, the main policymaking body of the ruling Communist Party.
Thang was sentenced to 31 years in prison for mismanagement in two separate trials for his role as chairman of PetroVietnam. He was the first former Politburo member to be imprisoned in decades.
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