The central bureau of investigation (CBI) team probing the Kunda triple murder case was attacked in Manikpur area of Pratapgarh district on Tuesday night.
The windscreen of the vehicle in which the CBI sleuths were travelling was damaged. No one was, however, injured in the incident.
Till the filing of the report, no complaint was registered by the CBI regarding the attack.
Talking to HT, a CBI officer said the team went to Manikpur town, around 15km from Kunda, to probe into the involvement of the mining mafia in the killing of the deputy superintendent of police (DSP) Zia-ul-Haq.
Some unidentified persons pelted their vehicle with stones while they were returning to Kunda where CBI has set up a camp office on the premises of the Nagar Panchayat office. The local police station was informed about the incident.
The CBI, which started investigation into the triple murders on Friday, has in its preliminary probe found that vehicles and machines used in the illegal mining of sand at Ghotni ghat on the banks of the Ganga were seized by the cops at Haque's instance.
Haque's widow Parveen Azad too has alleged that the mining mafia had threatened her husband. Gram pradhan Nanhe Yadav was also said to be involved in mining activities.