More than 50 children were burned, two of them seriously, when a man scaled the wall of a kindergarten in southwestern China and sprayed caustic soda on them.
Police detained a 23-year-old man about 40 minutes after the attack in Kaiyuan, Yunnan province, adding that they believed he was acting alone.
In a statement, the Kaiyuan municipal government said that at about 15.35pm, a man, surnamed Kong, cut wires and climbed over a wall into Dongcheng Kindergarten and sprayed sodium hydroxide on children and staff.
It said 51 pupils and three teachers were sent to Kaiyuan People's Hospital and PLA 926 Hospital for treatment. There were no life-threatening injuries, but two victims suffered serious burns, four had less serious burns and 48 sustained minor injuries.
The municipality said the suspect bought the substance online.
Initial inquiries indicated that the man was acting out of "revenge at society", but the investigation was continuing, the government statement said.
Kindergartens and primary schools have become targets in the past couple of years.
In September, a 40-year-old man was detained after eight pupils were killed and two more were wounded in a knife attack at Chaoyangpo Primary School in Enshi, central Hubei province.
In March a kindergarten teacher in in Jiaozuo city, Henan, was arrested for allegedly poisoning pupils' porridge, sending 23 of them to hospital.
In January, 20 pupils were wounded in a hammer attack by a former employee of Beijing No 1 Affiliated Elementary School at Xuanwu Normal School.
In October last year, a woman was detained for wounding 14 kindergarten children at a campus in Chongqing, southwestern China.
Copyright (c) 2019. South China Morning Post Publishers Ltd. All rights reserved.