Firefighters are battling nine large-scale forest fires on a total area of 107 hectares in the Irkutsk Region in East Siberia, the Russian forestry Service said on Sunday. \"According to satellite data, wildfires referred to the category of large-scale forest fires have been revealed in the Irkutsk Region,\" the service said. Over 161 people and 31 units of firefighting machinery are involved in combating the raging wildfires, the service said. Police in the city of Bratsk in the Irkutsk Region have opened criminal cases in the wake of wildfires that recently covered the city with thick smoke. The wildfires have caused the resignation of the acting head of the Bratsk administration, Alexander Tuikov and led to the concentration of harmful substances in the air exceeding normal levels. By Sunday most of the wildfires near Bratsk have been extinguished. Police have detained 20 people on suspicion of deliberate arson in forests near Bratsk. Wildfires across Russia are common during dry and hot summers and in the fall. Most fires start because of the careless behavior of local residents. Forest fires devastated a number of regions in central Russia last year, killing 62 people and leaving thousands homeless.