Eighty-three containers packed with rubbish were broken open at the Sihanoukville Autonomous Port by joint authorities on Tuesday.

The origin of the containers has yet to be ascertained, Ministry of Environment spokesman Neth Pheaktra said.

Pheaktra, who is also the ministry’s secretary of state, said officials were searching for the company or individuals behind importing the mostly plastic waste.

When found, the containers would be returned to the country or countries of origin, with those responsible to be punished, he said. “Fines will be imposed on the importing companies.”

Officials broke open the containers on Tuesday after they had been sitting at the Preah Sihanouk international port for some time.

Kun Nhem, the director-general of the General Department of Customs and Excise, Environment Minister Say Sam Al, Preah Sihanouk provincial governor Kuoch Chamroeun and Lou Kim Chhun, the director-general of Sihanoukville Port, were among the officials present during the operation, Pheaktra said.

He also hailed the operation as a testament to “good cooperation between the Ministry of Environment and other relevant authorities”.

“The ministry would like to thank all relevant parties, especially the General Department of Customs and Excise and the Sihanoukville Port Authority, for taking actions in cracking down on the violation in a timely manner and in rejecting the import of prohibited waste,” Pheaktra stressed.

Fake import documents said the containers held recyclables, but after being scanned in Cambodia they were found to contain nothing but plastic waste, a customs official involved in the operation was quoted by Fresh News as saying.

Speaking on condition of anonymity, the official said the containers had been shipped to the port in stages and that the authorities were still finding out whether the waste contains “radioactive substances”, while likening the case to that of the Philippines.

According to AFP, the Philippines returned about 69 containers of waste back to Canada last month, putting an end to a diplomatic row between the two countries.

The rubbish had been stored in dozens of containers which a Canadian firm sent to the Philippines in 2013 and 2014 – ostensibly for recycling, the news agency added.

Last week, Indonesia said it would send more than 210 tonnes of garbage back to Australia after the authorities found hazardous material and household trash including plastic bottles and packaging, used diapers, electronic waste and cans in eight containers seized in Surabaya, the country’s second largest city.

In May, Malaysia announced it was shipping 450 tonnes of imported plastic waste back to its sources, including Australia, Bangladesh, Canada, China, Japan, Saudi Arabia and the US.

Pheaktra stressed that Prime Minister Hun Sen had previously highlighted “many times” that “the Royal Government of Cambodia does not allow any import of plastic waste to be processed in the Kingdom.

“Cambodia is not a dustbin to where other countries can dispose of out-of-date e-waste, and the government always objects to any import of plastic waste and lubricants to be processed in the country.”