A kindergarten teacher has been arrested in eastern China after 23 students took ill in a suspected act of deliberate poisoning, police said.

Key points: The children's food was contaminated with sodium nitrite

The children's food was contaminated with sodium nitrite Children began vomiting and fainting after eating porridge

Children began vomiting and fainting after eating porridge Police are still looking for a motive for the attack

The teacher, identified by the surname Wang, is believed to have adulterated the children's food with sodium nitrite, the Jiaozuo city police said on their official microblog.

Overexposure to sodium nitrite can be toxic and possibly fatal.

Police said they were still looking for a motive in last week's incident.

However, the BBC reported that Chinese media quoted police that the suspect had sought revenge on a colleague.

Children began vomiting and fainting after eating their breakfast at school, the BBC said, and one parent said doctors had pumped his child's stomach at hospital.

Schoolchildren in China have been the target of often fatal attacks by people bearing grudges or considered mentally ill.

The children fell ill after being served rice porridge for breakfast at kindergarten. ( Flickr: Su-lin )

In 2002, 42 people, mostly schoolchildren, died after eating snacks laced with rat poison in the eastern city of Nanjing.

The killer, who apparently was jealous of his rivals' thriving business, was swiftly sentenced to death and executed.

AP