The deaths occurred in three districts of the impoverished northern state, where temperatures have hovered around 45 degrees Celsius in recent days, senior health official Vijay Kumar told AFP.
Severe heat has left dozens dead over a 24-hour period in India's Bihar state, as the country enters a third week of searing temperatures, officials said Sunday.
The deaths occurred in three districts of the impoverished northern state, where temperatures have hovered around 45 degrees Celsius (113 Fahrenheit) in recent days, senior health official Vijay Kumar told AFP.
Forty-nine people died in three districts of the Magadh region that has been hit by drought, he said.
"It was a sudden development on Saturday afternoon. People affected by heatstroke were rushed to different h ospitals," Kumar added.
"Most of them died on Saturday night and some on Sunday morning during treatment."
Kumar said about 40 more people were being treated at a government-run hospital in Aurangabad.
"Patients affected by heat stroke are still being brought, the death toll is likely to increase if the heatwave continues."
Most of the victims were aged above 50 and were rushed to hospitals in semi-conscious state with symptoms of high fever, diarrhoea and vomiting.
Twenty-seven people died in Aurangabad district, 15 in Gaya and seven in Nawada district, officials said.
State Chief Minister Nitish Kumar has announced a compensation of $5,700 (400,000 rupees) for the family of each victim.
Harsh Vardhan, India's health minister, said people should not leave their homes until temperatures fall.
"Intense heat affects brain and leads to various health issues," he said.
Large parts of northern India have endured more than two weeks of sweltering heat. Temperatures have risen above 50 degrees Celsius (122 Fahrenheit) in the desert state of Rajasthan.
A heatwave in 2015 left more than 3,500 dead in India and Pakistan.
In 2017, researchers said South Asia, which is home to one fifth of the world's population, could see heat levels rise to unsurvivable levels by the end of the century if no action is taken on global warming.