The accused, including slain village head Nanhe Yadav's brothers Pawan and Phoolchandra, son Babloo and private security guard Manjeet were arrested by the CBI in Pratapgarh district on Saturday.
All the four accused were produced before the court of remand magistrate Niyaz Ahmad Ansari, which remanded Pawan, Phoolchandra and Manjeet to judicial custody till April 28.
Balipur village head Nanhe Yadav, his brother Suresh and DSP Zia-ul-Haq were killed on March 2 in Pratapgarh, triggering a public outrage after which the Samajwadi Party government handed probe to the CBI.
Later, Parveen, widow of DSP Zia-ul-Haq, had accused then UP minister Rahuraj Pratap Singh of being the key conspirator in the murder of her husband.
She had lodged an FIR against the minister, after which Raghuraj was forced to quit the Akhilesh Yadav government.