Extreme heat has killed at least 96 people in India's most populated states. Authorities have advised vulnerable members of the public to stay indoors to prevent exacerbating pre-existing health concerns.

According to officials, the fatalities were largely adults over the age of 60 who had preexisting health difficulties in the northern state of Uttar Pradesh and eastern Bihar. All 54 deaths in Uttar Pradesh happened in the Ballia area, where hospitals have seen a constant stream of people seeking treatment for heat-related illnesses like high fever, vomiting, diarrhea, as well as respiratory and heart problems.

Read more: Global warming sharply escalated the risk, severity of heat in UK

Brijesh Pathak, the state's health minister, has launched an investigation into the high number of fatalities in the state. The BBC reported on Monday that local administrations have come under fire from the opposition for "carelessness" in failing to warn the people about the possible health consequences of the heatwave.

A local resident RS Pathak told AP that "this has never happened in Ballia," adding that "People fear venturing out. The roads and markets are largely deserted.”

Ballia recorded a maximum temperature of 43 degrees Celsius (109 degrees Fahrenheit) on Sunday, which is around 5 degrees Celsius more than the typical average. A humidity of 25% worsens the heat.

India's Meteorological Department stated on Sunday that no relief was expected to come in the next day, implying that the heatwave will last until Monday. Meanwhile, 42 people have died in Eastern Bihar in the last few days. On Saturday, temperatures in Patna, the state capital, were barely below 45 degrees Celsius (113 degrees Fahrenheit).

The summer season from May to June is usually the hottest time in India. However, during the last decade, the country has seen abnormally high, increasing heat, which frequently causes water shortages in the country of 1.4 billion people.

An academic group conducted a study earlier this year that showed that human-induced climate change has rendered extreme heatwaves in South Asia roughly 30 times more likely. According to a study published in the scientific journal The Lancet, heat-related mortality in India increased by 55% between 2000 and 2021.