They march like a sea of people, walking toward the spot where they take holy baths, drawn by the hope that the bathing would bring them salvation.But when they leave — believing their sins have been cleansed by the redemptive bath — they leave with one thing in common: their foreheads display a sacred stroke of color.

At least 30 people have been killed and many more were injured in a stampede at the world’s largest religious gathering in India, police said. The tragedy took place as millions of pilgrims rushed to dip in sacred waters during the Maha Kumbh festival in the north of the country.