The plastics can partially replace metals such as copper and zinc and have various applications including in auto parts, electronics, and medical equipment, the ministry said in a statement.

The investigation should be completed in a year but could be extended for six months, it said.

The European Commission, which oversee EU trade policy, said it would carefully study the contents of the investigation before deciding on any next steps.

"We expect China to ensure that this investigation is fully in line with all relevant WTO [World Trade Organization] rules and obligations," a spokesperson said.

China's plastics probe comes amid a broader trade row with the United States and Europe.

The United States on Tuesday unveiled steep tariff increases on Chinese electric vehicles (EVs), computer chips, medical products and other imports.

On Friday, the European Union launched a trade investigation into Chinese tinplate steel, the latest in a string of EU trade and subsidy probes into Chinese exports.

Most notably, the European Commission launched a probe last September to decide whether to impose punitive tariffs on cheaper Chinese EVs that it suspects of benefiting from state subsidies.

Beijing argues the recent focus by the United States and Europe on the risks to other economies from China's excess capacity is misguided.

Chinese officials say the criticism understates innovation by Chinese companies in key industries and overstates the importance of state support in driving their growth.