"Chhath formally began with age-old 'nahai-khai', a ritualistic bath before preparing a traditional meal of boiled rice and pumpkin," said devotee Nirmala Devi.
She is a 'varti' - one who performs the Chhath prayers and follows age-old rituals associated with it.
"The banks of river Ganga, Punpun, Gandak and Kosi as well as big and small water bodies were crowded as devotees prepared vegetarian food on handmade earthen 'chulhas' (cooking stove)," a police officer said.
Chhath is celebrated six days after Diwali. It is dedicated to the Sun god, and is one of Bihar's most popular festivals.
Chhath is celebrated six days after Diwali. It is dedicated to the Sun God.
Sarita Devi, another varti, said they used only dry wood from mango trees and bamboo baskets for cooking.
After nahai khai, another ritual 'kharna' is observed when 'kheer' will be cooked and distributed among neighbours, friends and relatives, followed by main offerings of argya to the setting Sun Friday and rising Sun Saturday.
During the festival, married women observe a fast for 36 hours and devotees traditionally offer wheat, milk, sugarcane, bananas and coconuts to the Sun.
The administration, along with voluntary organisations, is working to manage the crowds and keep the area around the river banks clean.
"District authorities have been asked to accord top priority to the safety of devotees," an official said.
Bihar Chief Minister Nitish Kumar asked officials to keep river banks clean and to tighten security in view of the serial blasts in Patna last month.