The second stage of oil and conventional gas exploration in Bulgaria's Provadia Block has been met with opposition by local residents.

The exploration activities are part of a project for studying the Provadia Block which was launched in 2011.

On Tuesday, however, the work of the contractors was delayed by a spontaneous protest of the residents of the villages of Ovcharovo and Kostna Reka, who voiced worries over environmental pollution and health risks.

The machines conducting seismic exploration have been on the territory of the villages since the beginning of the week, with locals insisting that they were never informed about the drilling.

The company contracted to conduct the oil and gas exploration activities insists that it informed all mayoral administrations in the region.

Stoyan Katsarov, supervisor of the exploration activities, firmly rejects allegations of a negative environmental impact.

He assures that the seismic testing poses no risks to the environment, adding that the technology is used all over the world.

The exploration activities near the northeastern city of Shumen will continue for another month and the presence of oil and conventional gas fields in the region will be determined in a few months' time.