New Delhi: A massive explosion ripped a boiler at the state-run power giant NTPC 's Unchahar plant in Uttar Pradesh's Rae Bareli district, killing at least 20 people and injuring nearly 100, officials said.The NTPC initiated a probe to ascertain the reasons behind the blast, while Chief Minister Yogi Adityanath announced Rs 2 lakh compensation for the families of those killed and Rs 50,000 for the grievously injured, they added."Twenty deaths have been confirmed by the district administration. Twenty-two people with severe burns have been referred to Lucknow. Another 15 are admitted to a Rae Bareli hospital," UP's ADG (Law and Order) Anand Kumar said.He said that the number of casualties could rise.Principal Secretary (Home) Arvind Kumar said that 90-100 people were injured in the blast.In a statement, the National Thermal Power Corporation (NTPC) said that at unit number six of its Unchahar plant, there was a sudden abnormal sound at 20-meter elevation around 3:30 in the afternoon.There was an opening in corner number two from which hot flue gases and steam "escaped" affecting the people working around the area, the central public sector undertaking said.It added that around 80 people were rushed to NTPC hospital, most of whom were discharged after first-aid.The 1,550-MW plant supplies electricity to nine states, according to officials, and employs around 870 people.Prime Minister Narendra Modi said he was "deeply pained" by the accident at the power plant and added that the situation was being closely monitored."Deeply pained by the accident at the NTPC plant in Raebareli. My thoughts are with the bereaved families. May the injured recover quickly. The situation is being closely monitored & officials are ensuring normalcy is restored: PM @narendramodi," the prime minister's office tweeted.Union Power Minister R K Singh, through social media posts, expressed deep anguish at the loss of lives and said that he had directed NTPC Chairman and Managing Director Gurdeep Singh to rush to the site.The Unchahar sub-division in Rae Bareli, which is represented by Congress president Sonia Gandhi in Parliament, is around 110 km from the state capital.ADG Kumar said that all available ambulances were pressed into service, and the additional district magistrate and the additional superintendent of police were on the spot to supervise relief and rescue operations.Chief Minister Adityanath, on a three-day official visit to Mauritius, ordered that necessary steps be taken for rescue and relief.The chief minister has taken cognisance of the Unchahar accident and has directed the principal secretary (home) to ensure that all steps were taken for rescue and relief, principal secretary (information) Awanish Awasthi, who is accompanying Adityanath, said."The chief minister expressed his condolences over the deaths of workers in the Unchahar NTPC unit and announced Rs 2 lakh compensation for the family of those killed and Rs 50,000 for the grievously injured, besides Rs 25,000 for other injured workers," Awasthi said.A National Disaster Response Force (NDRF) team was also despatched to the explosion site from the state capital for relief and rescue operations, an official said.The explosion triggered panic among the employees who ran helter-skelter. Such explosions can generate searing heat, an official said.An injured employee undergoing treatment at a hospital said that a sudden gush of hot gas with contents of ash-like material engulfed him at the NTPC plant.The man said he was unable to understand what had happened and found himself on a hospital bed with his body scalded all over, when he regained consciousness.The plant area was cordoned off by the police to facilitate smooth running of ambulances. Two companies of the Uttar Pradesh Provincial Armed Constabulary (PAC) have been sent to the plant as reinforcement.Congress president Sonia Gandhi expressed shock and horror at the "terrible tragedy" in her Lok Sabha constituency. Conveying her deepest condolences to the families of the bereaved, Gandhi urged upon the authorities to provide immediate medical assistance to the injured.Congress vice-president Rahul Gandhi will take a break from election campaign in Gujarat to visit Rae Bareli tomorrow to meet the families of the victims."Due to the unfortunate NTPC accident , I will visit Rae Bareli tomorrow morning," he said on Twitter.District Magistrate Sanjay Kumar Khatri told PTI that 40 ambulances were immediately pressed into service.Chief Medical Officer of Rae Bareli D K Singh, along with a team of 10 doctors, was deployed to carry out immediate treatment to the injured, the district magistrate said.He also said that arrangements have been made to bring the serious cases to KGMU Hospital and the Civil Hospital in Lucknow. Some of the injured were being sent to Rae Bareli, Khatri said.CMO Singh said that, if necessary, some of the critical cases could be referred to Delhi by air ambulance.