One of the world’s largest rivers, the Brahmaputra, which flows into India and neighboring Bangladesh from Tibet, burst its banks in Assam over the last three days, inundating more than 1,500 villages.

Torrential rains lashed most of the rugged state, and the downpour continued on Wednesday, with more forecast over the next two days.

Authorities said on Wednesday that more than 500,000 people have fled their homes in India’s northeastern state of Assam to escape heavy floods triggered by pre-monsoon rains that drowned seven, as they warned the situation could worsen.

“More than 500,000 people have been affected, with the flood situation turning critical by the hour,” Assam’s water resources minister, Pijush Hazarika said.

“The situation remains extremely grave in the worst-hit Dima Hasao district, with both rail and road links snapped due to flooding and landslides,” said Assam’s revenue minister, Jogen Mohan, who is overseeing relief efforts there.

Water levels in the Brahmaputra were expected to rise further, national authorities said.

Cities elsewhere in India, notably the capital, New Delhi, are broiling in a heat wave.