Southeast Asia has been flooded with waste plastic from more developed nations such as the US, Australia and Britain since last year when China -- which boasted a massive recycling industry -- ordered a halt to imports.
Malaysia has been particularly hard hit as many recyclers from China moved there as the ban took effect.
The government has already sent back at least 10 containers of plastic waste to different countries and closed down 155 illegal processing plants, senior environment ministry official K. Nagulendran said at the Foreign Correspondents' Club of Malaysia on Thursday.
But officials are struggling to identify the origin of 198 more containers thought to contain scrap plastic at three ports.
The contents have been declared a type of plastic which can legally be imported, but none of the containers had the necessary permits to enter the country, he said.
"We have been limited with finding the country of origin, because they have just abandoned them," said Nagulendran.
Several Southeast Asian countries have sent back unwanted waste in recent months, including the Philippines -- which returned a huge shipment of garbage to Canada -- and Indonesia, which shipped five containers to the US.