Pilgrims prepare for holiest day at India's Kumbh Mela on Ganges Millions of Hindu pilgrims are attending the Maha Kumbh festival, which is one of the world's largest religious gatherings that lasts 55 days and falls every 12 years. During the festival pilgrims bathe in the holy Ganges River in a ritual they believe can wash away their sins. TENS of millions of Hindu pilgrims prepared to cleanse their sins with a plunge into the sacred river Ganges, ahead of the most auspicious day of the world's largest religious festival. Some 30 million Hindu saints, devotees and visitors were expected to take part in the Kumbh Mela on Sunday -considered the holiest of the 55-day festival - in north India, police said. "One dip in the river has the power to change life forever," said 65-year-old Malti Devi from London, taking part in the festivities for the first time. The Kumbh Mela, which began last month, takes place every 12 years in Allahabad in northern Uttar Pradesh state, with smaller but similar events every three years in other locations around India. Indian Hindu devotees dry their cloths after a holy dip at Sangam, at the confluence of the Rivers Ganges, Yamuna and mythical Saraswati, during Maha Kumbh festival, in Allahabad, India. It has its origins in Hindu mythology, which tells how a few drops of the nectar of immortality fell on the four places that host the festival - Allahabad, Nasik, Ujjain and Haridwar. Devotees believe entering the mighty river cleanses them of sin and frees them of the cycle of birth and rebirth. Many believe some three billion Hindu deities will also take a dip in the sacred river to bless mankind on Sunday. The festival, which draws ash-covered holy men, a smattering of international celebrities as well as millions of ordinary Indians, welcomed new waves of devotees. Naked ash-smeared mystics, known as sadhus, and swamis and gurus clad in flowing robes streamed into the festival grounds. An Indian devotee holds her child as a man shaves his head on the banks of the river Ganges. Some male Hindus have their heads shaved in a show of sacrifice at religious festivals. Today, when the water is considered the holiest and most auspicious, is "the most crucial day for the pilgrims and for police," Ajit Tyagi, said a police officer in Allahabad. We have to make sure everyone is safe. Over 7000 policemen have been deployed to oversee today's bathing ritual, along with 30,000 volunteers, he said. A devotee dries saris on the banks of the Ganges river after at the Kumbh Mela in Allahabad. The "safety of women and children is our first priority," said Mr Tyagi, adding that over 10 million women were expected to participate in the big bathing day. Increasing pollution in the river has been another key concern for authorities who said they are constantly monitoring levels since the festival began on January 14. Ms Devi said she would donate food and clothes to the poor after taking the ritual dip in the river. A hindu holy man or Sadhu prays while standing on one leg at the banks of the river Ganges at the Kumbh Mela. I'm not worried about the security or pollution. We're here to celebrate a festival that brings the rich and poor together," she said. Around eight million people housed in a sprawling city of tents have already bathed at the confluence of the Ganges and Yamuna rivers since the festival started. Ahead of the Kumbh Mela, Indian Prime Minister Manmohan Singh had warned of action against industries polluting the river and ordered the release of water from India's highest dam in Tehri to meet demands for the festival. "No one will be allowed to wash their clothes or throw plastic bags in the river on the main bathing day," said Manikant Mishra, an administrator at the Kumbh Mela. "Take a dip and move out of the water - those are the instructions we are giving," Mr Mishra said.