Mustafa Bozbey, mayor of Türkiye’s fourth largest city, Bursa, for the main opposition Republican People’s Party (CHP) was detained on Tuesday, along with 54 other suspects. Authorities said Bozbey and others face charges of running a criminal organization, bribery, money laundering and zoning violations. The Sabah newspaper reported that Bozbey’s wife, daughter and brothers were among other detainees.

The Chief Prosecutor’s Office in northwestern Türkiye said an investigation was underway against Bozbey and others on allegations that the mayor, during his tenure as mayor of Nilüfer, a district of Bursa, was involved in taking bribes in return for illegally changing zoning plans. The statement said Bozbey’s successor as Nilüfer mayor, Turgay Erdem, was also involved in the scheme. Erdem was arrested in a similar operation last year.

Prosecutors said Bozbey was the leader of a criminal ring, adding that four other suspects wanted in the same probe were at large.

The main opposition CHP is under mounting scrutiny as a wave of corruption, bribery and terrorism-related investigations sweeps across its municipalities.

Authorities say several major investigations are underway into municipalities controlled by the CHP, covering allegations from large-scale tender rigging and bribery to financing terrorist organizations.

The most extensive probe targets the Istanbul Metropolitan Municipality (IBB), led by ousted Mayor Ekrem Imamoğlu, over claims of systematic corruption, fictitious tenders and abuse of public resources. Prosecutors allege a network, headed by senior municipal officials, rigged numerous public contracts. Imamoğlu and his aides deny all charges.