SHANGHAI, July 23 -- Police in Shanghai have detained two people suspected of murdering an infant with cleft lip, including a doctor and the toddler's grandfather, authorities said Thursday.

Doctors with the No. 2 People's Hospital in Chongming County alerted police last Friday when they found the baby boy dead during a night inspection. The baby had been born only two days earlier.

Initial investigations show that the baby's grandfather had obtained potassium chloride from an obstetrics doctor with the hospital and injected the chemical compound into the baby's head, local police said.

Potassium chloride is usually used to treat potassium deficiency. Direct injection can cause cardiac arrest.

Further investigation is under way.

Cleft lip and palate is one of the most common congenital birth defects, with about one in every 1,000 children born in China affected by the condition.

In China, the average cost of corrective surgery for cleft palate can be as much as 10,000 yuan (1,633 U.S. dollars). With an incomplete medical assistance system and millions of people struggling under the country's poverty line, some parents have killed or abandoned babies with birth defects.

In May, doctors saved a baby with cleft palate found alive in the wild in Tiandong County in south China's Guangxi Zhuang Autonomous Region, ten days after he was abandoned by family members.