The ministry says it's received complaints from chemical firms about foreign dumping in the Chinese market, specifically a tough polymer called polyformaldehyde copolymer.

It's strong enough to replace metal in some machinery.

And Taiwanese makers of the substance, alongside those from the US, EU and Japan, will be subject to a Chinese trade probe.

The probe will look at whether foreign firms dumped in the Chinese market between 2021 and 2024.

It will take at least a year, and it's unclear what sanctions foreign firms could face in the end.

But for Taiwan firms at least, the stakes are high.

During that period, they sold over two million US dollars of the material to China, amounting to 60 percent of their exports.

While Taiwanese firms aren't the only target, some in Taiwan find their inclusion suspicious.

China claims Taiwan as part of its territory, and has sanctioned a range of Taiwanese products in recent years, including fruit and seafood.

It's something Taiwan sees as an attempt to pull it closer into Beijing's orbit.

Some see a repeat of this tactic just as Taiwan inaugurates its next president.

Taiwanese makers have 20 days to respond to China's announcement, and Taiwan's economy ministry says it will help them to do so, and find alternate markets.

Still, researchers say Taiwanese firms face a tough road ahead.

Whatever Beijing's motives and intentions, the probe is a sign that cross-strait trade friction will continue, even as Taiwan welcomes a new president.

Luffy Lee and John Van Triest for Taiwan Plus.

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