Eighteen people were wounded in an explosion that rocked a Combined Heat and Power Plant (CHPP) in the city of Shagonar of Russia's Tuva Republic on Wednesday morning, local authorities said.

"At present, 18 people have been hospitalized. Of these, six are in critical condition. All the injured are currently being transported to hospitals in Kyzyl," Vladislav Khovalyg, head of the Tuva Republic, was quoted as saying by the TASS news agency.

The CHPP had 21 people working at the time of the explosion. Search operations are currently underway to locate the remaining three individuals, according to TASS.

The explosion was confined to the fuel supply point with a belt container in the boiler room building. The boilers remained intact, and the fire was contained within an area of 50 square meters, the TASS report quoted the regional Ministry of Emergency Situations as saying.

(A distant view of a Power Station in Sverdlovsk Oblast, Russia, June 21, 2017. /CFP)