The Hindu festival that turned deadly in northern India on Wednesday is a religious gathering with deep spiritual meaning for devotees who come by the millions to take a cleansing dip in waters they consider sacred.

More than seven people were killed in a stampede at the Maha Kumbh Mela, or Great Pitcher Festival, in the northern Indian holy city of Prayagraj on Wednesday.

Officials had been preparing for months for the world’s largest religious festival, with around 400 million Hindu pilgrims expected to take part