The pilgrims come and go as strangers. 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 17 people were killed and many more injured in a stampede at India's Maha Kumbh festival, the world's largest religious gathering, a doctor at a government hospital said, as tens of thousands of pilgrims rushed to dip in sacred river waters during the Hindu event.

Indian authorities have ordered a probe into the stampede at the Maha Kumbh Mela Hindu festival that killed dozens of devotees on Wednesday as millions gathered for a "holy dip" in sacred river waters as part of the six-week event,