WASHINGTON (Reuters) - The U.S. government on Monday said domestic producers were being harmed by imports of fabricated structural steel from China and Mexico, and that it would instruct the customs agency to collect cash deposits from importers of such steel.

The U.S. Commerce Department said it had found that imports from Canada were not being unfairly subsidized.

Mexico said in a statement that a U.S. countervailing duty investigation of Mexican fabricated structural steel was an "ordinary" anti-dumping probe with no relation to earlier tariff threats by U.S. President Donald Trump.

Mexico added that its economy ministry would defend the interests of the companies under investigation, and that it had been actively participating in anti-subsidy procedures since early 2019. It did not give further details in the statement.

The preliminary subsidy determination does not endanger ratification of the new North American trade deal, Mexico's deputy foreign minister for the region, Jesus Seade, said on social network Twitter.That deal was designed to replace the North American Free Trade Agreement that governs more than $1.2 trillion of mutual trade.

The U.S. International Trade Commission said in March that imports of fabricated structural steel from Canada, China and Mexico were harming domestic producers.

Fabricated structural steel is used in major building projects, such as bridges, buildings, parking decks and ports. An industry trade group had filed a petition asking for the trade case to be launched.

In 2018, the United States imported $722.5 million worth of fabricated structural steel from Canada, $897.5 million worth from China and $622.4 million worth from Mexico, according to the Commerce Department.

The department is expected to make its final ruling on the imports around Nov. 19.