It took only an hour for the silent alarm to be triggered after Nanjing Children's Welfare Institution opened its "safe haven" for abandoned babies on Tuesday.

Jin Jiangying, the nurse on duty, rushed to the small but secure building and found a newborn boy wrapped in a colorful blanket.

He had been left in a crib provided at the haven along with feeding bottles, milk powder, diapers and clothing.

"He was asleep when I arrived. His belly looked swollen and he's had a fever since Wednesday morning," Jin said, adding that the baby's umbilical cord was still attached when he was discovered.

Medical workers at the institution said the boy was less than 7 days old. He was sent to Nanjing Children's Hospital.

Had he been abandoned outside in the winter cold, like many children in the past, Jin said there was a good chance the infant may not have survived.

Guards at the institution were alerted by an infrared sensor, which triggers an alarm after three minutes, allowing time for the person abandoning a child to leave.

The 5-square-meter safe haven, which cost 70,000 yuan ($11,450) to build, has an incubator, a crib, bedding and an air conditioner. However, there are no surveillance cameras.

Xie Jun, director of nursing at the institute in the provincial capital of Jiangsu, said, "Every year, more than 160 children are abandoned outside the front door."

The province plans to open a second safe haven in Xuzhou next year.

Nineteen provinces have built, or plan to build, safe havens for abandoned children, said Li Bo, director of the China Center for Children's Welfare and Adoption, the organization pushing the safe haven concept.

Each province should set up one or two safe havens at child welfare centers in its capital or other large cities before the end of next year, he said.

Dou Yupei, vice-minister of civil affairs, said at a news conference that safe havens follow the principle of "life first, and give priority to children's rights".

Under Chinese law, those who abandon dependents face a prison sentence of up to five years.

"In China, abandoning children is illegal and immoral. Therefore, parents or others choose to leave babies secretly at places that are hard to find." Dou said. "Because of this, some babies die before they are found, or the conditions of some sick babies worsen."

On Nov 6, an abandoned newborn baby froze to death in Xuanwu Lake Park, Nanjing.

Earlier this month, a newborn boy was abandoned at a dust heap in Beijing's Tongzhou district and died before paramedics arrived, media reports said.

A children's welfare institute in Shijiazhuang, capital of Hebei province, set up the country's first safe haven in 2011.

The Ministry of Civil Affairs told civil affairs local authorities to start pilot projects in July this year.

Concerns have been raised that the move may encourage irresponsible parents to give up their children.

However, Tong Xiaojun, a professor at China Youth University for Political Sciences specializing in child rights, said abandoning a child is often the last resort.

"Providing safe havens will not necessarily result in increasing numbers of abandoned children, but they can protect lives," she said.

She said she believes the government should improve services to better protect abandoned children by asking those who leave a baby in a safe haven to provide a medical history about the baby's parents and their contact information.

"This can help medical personnel to better treat the baby for health problems, but the information should be confidential," she said.