Severe heatwave killed 12 more people in Bihar in the past 24 hours, taking the death toll over the past three days to 90, official said on Tuesday.However unofficially, the heatwave has claimed more than 250 lives in three days across a dozen districts.Deaths were reported from Aurangabad, Gaya, Nawada and Jamui districts, where temperatures hovered around 45.8 to 42 degrees Celsius on June 15, 16 and 17.According to the State Disaster Management Department website, some 90 deaths had been recorded till Tuesday. Of these, Aurangabad recorded 41 deaths, Gaya 35 and Nawada 14.In a first, prohibitory orders have been imposed in the wake of extreme weather conditions under Section 144 of the Code of Criminal Procedure (CrPC) in Gaya, Begusarai, Darbhanga, Gopalganj, Madhubani and Sitamarhi districts Bihar Chief Secretary Deepak Kumar told the media here that the government will conduct an enquiry into how intense the heatwave was between 3-5 p.m. on June 15 that it resulted in the highest number of deaths in a day due to heatstroke.Kumar said the Chief Minister had also ordered an environment survey of the state over the next four days.Chief Minister Nitish Kumar has already announced a compensation of Rs 4 lakh to the kin of the victims.The government has also issued a heat alert and advised people to avoid going out during the day time.Additional Health Director of Magadh range Dr Vijay Kumar said that nearly 100 people had been admitted in government-run hospitals in Gaya, Aurangabad and Nawada, while dozens were being treated at primary health centres in the three districts.