Authorities in eastern China have concluded that newborn boy rescued from sewer pipe was trapped by accident

The mother of a newborn baby rescued from a sewer pipe in eastern China will not face criminal charges, authorities have said.

The little boy – known only as Baby 59 – has been released into his grandparents' care, the official China News Service reported, citing police. Earlier reports said his mother had custody.

His case sparked a wave of sympathy around the world when footage of his rescue by firefighters and medics emerged. At first, officials in Pujiang county, Zhejiang province, said they were treating it as attempted murder, believing that he had been abandoned.

But they have now concluded that he was trapped by accident, after it emerged that the resident who raised the alarm was in fact his mother. The unmarried 22-year-old had hidden her pregnancy and secretly delivered the baby on Saturday in the shared bathroom; she said he had slipped into the squat toilet by accident.

An official in Pujiang county's propaganda office told Associated Press on Thursday that police concluded the woman did not initially identify herself as the mother out of fright.

Zhang Jianbo, the head of Punan police station, told China News Service that the woman's parents were now caring for the baby, who suffered minor cuts and bruises but is otherwise healthy. He added that the man believed to be the father had been found and that a paternity test would be carried out.

Earlier, authorities told AP that the baby had been released into the care of his mother and a man claiming to be his father, while Xinhua said that both the mother and her parents would care for him.

Wellwishers had inundated officials with offers to adopt the little boy.

"Even if some other people wanted to adopt this baby, since his mother is still there, it would be a very complicated and hard process for other people to adopt him," said Xiong Bingqi, deputy director of the independent 21st Century Education Research Institute.

But he said the baby's care would not be supervised by social workers, as would be expected elsewhere.

"The baby returns to her. This case is done," he said.

"This case shows our child protection law is struggling … If the government removes the baby from its parents, they should take responsibility for caring for him. But the government's allocated funds are limited and charity organisations can only receive a certain number of children, when their parents cannot be found.

"If the children have parents, the government prefers to ask their parents to take the responsibility. The local government does not have enough funding to establish a social security system to help those children when their parents are not doing a good job."

Local media earlier reported that the woman became pregnant after a one-night stand and that the father had denied paternity. She told officials she could not afford an abortion and had hidden her pregnancy from her parents.

While premarital sex is common in China, unmarried motherhood still bears a stigma. Critics say sex education is also inadequate.