PINGLIANG - A local couple was accused in a milk poisoning case that left three children dead and 36 others sickened in northwest China's Gansu Province, authorities said Monday.

The government of Pingliang City, where the incident occurred last week, held a press conference Monday afternoon at which it partially revealed the identities of the two suspects.

Related readings:  Suspect accused of intentionally poisoning milk  Milk was poisoned 'deliberately'

Thirty-nine people in Pingliang were sent to the hospital after drinking nitrite-tainted milk on Thursday. Three children younger than two years old died, the youngest of them was 36 days old.

Investigators found that nitrite, an industrial salt that can be deadly, had been added to fresh milk from two dairies.

Police said Sunday that the tainted milk incident was a case of intentional poisoning and they had taken the suspects into custody.

The suspects, a man with the surname Wu and his wife, surnamed Ma, are residents of Jingtan Village, Liuhu Township in Kongtong District, said Wu Zhentu, a spokesman for the city government.

He did not reveal any further information about the couple at the press conference and refused to take any questions from reporters.

The spokesman also did not disclose the motive for the crime at Monday's news briefing, but according to villagers who live near the farms, vicious competition among farm owners might be involved.

As of Monday afternoon, 31 people have been discharged from the hospital, and the remaining five people hospitalized are in stable condition, Wu said.