"Chhath Puja began with ritualistic bath, before preparing the traditional meal of boiled rice and pumpkin on earthen stove," said Sudha Devi, a devotee, while cooking the traditional meal at Collectorate Ghat near the Ganga river in Patna.
Dressed in new cotton sari, Sudha is one of the million devotees across the state who thronged the Ganga and other water bodies since early Monday morning.
"We have to first take bath and prepare the meal. We then perform the rituals of 'Nahai-Khai' (first day of the festival) that marks the beginning of Chhath Puja," said Krishna Sinha, another devotee who with her family members was preparing food at Gandhi Ghat.
She said: "Nahai-Khai is a symbol of purity and strict discipline. It will be followed by 'kharna' Tuesday, when 'kheer' will be prepared and distributed among neighbours, friends and relatives."
Krishna Sinha said she will keep fast and pray for the next three days. On Wednesday evening, devotees will offer prayers called 'argya' to the setting Sun and follow this up by offering prayers to the rising sun Thursday morning.
Some devotees prefer to take bath in their own houses due to dirty river banks and polluted river waters.
Chhath Puja is celebrated on the sixth day following Diwali and is dedicated to the Sun. It is one of the most popular festivals in Bihar.
During the festival, women observe a continuous fast for 36 hours. Devotees offer wheat, milk, sugarcane, bananas and coconuts to the Sun.
"District magistrates have been directed by (Chief Minister) Jitan Ram Manjhi to give top priority to safety and security of devotees," an official said.
In Patna, about 200 divers have been deployed to handle any emergency near the river banks and over 5,000 policemen have been deployed to monitor ghats and roads.