Police have investigated 44 people suspected of violating laws and regulations during a protest against the construction of a petrochemical project in Maoming, Guangdong province.

Eighteen have been detained for further criminal investigation and 26 have received administrative punishment, according to Zhou Peizhou, Maoming's deputy police chief.

"They have been detained and punished for disturbing social and public order," Zhou told a news conference on Thursday afternoon.

Zhou refuted rumors that 15 people were killed and more than 300 others were injured during a police operation to disperse the protesters.

Liang Luoyue, deputy mayor of Maoming, said the protest started on Sunday morning when around 1,000 people rallied to protest against construction of a paraxylene project.

The protesters then threw stones, eggs and water bottles at police.

"At around 8 pm on Sunday, about 40 people illegally stopped two cars, overturning one of the vehicles, and beating police officers who tried to stop them," Liang said.

"After they were dispersed by police, the suspects then began destroying billboards and windows of shops along local streets and later burned a police car, which was on patrol at about 10 pm.

"The illegal and intentional destruction of public property has violated laws and regulations and is a public order offense."

Order was restored after officials met the protesters on Monday and Tuesday.

Liang met protesters in the city government building on Tuesday. He listened to their suggestions for the project and answered their questions.

The protesters fear construction of the PX project will damage the environment and harm people's health.

Liang promised not to start construction of the petrochemical project until an agreement has been reached with local residents.

Liang Bo, an official with Maoming health and family planning bureau, said 15 people, including four police officers, were sent to hospitals for treatment after the protests.

"Eight of them have been discharged," Liang Bo said.

The proposed 3.5 billion yuan ($569 million) PX project would be an addition to the city's petrochemical operations jointly run by the local government and State-owned oil giant Sinopec.

Maoming, a coastal city, is a major petrochemical production base in Guangdong.

zhengcaixiong@chinadaily.com.cn