Tesla, Inc. (TSLA  ) is reportedly facing an adverse development in Sweden as workers at four major ports in the country are striking against the electric vehicle maker.

What Happened: The strike, which was on in Malmö, Trelleborg, Gothenburg, and Södertälje, is on the verge of expanding to all Swedish ports, Teslarati reported, citing local media reports.

IF Metall, a powerful union in Sweden, reportedly warned Tesla that it would go on strike if the Elon Musk-led company did not agree to sign a collective agreement with its striking mechanics. The dock workers reportedly joined in on Tuesday to show their solidarity and have refused to load and unload Teslas.

With Tesla reportedly trying to get around the blockade by using the other parts, striking dock workers' unions are looking to close the possibility.

The report also noted that Fastighets, another union, has said it would not clean Tesla premises in Huddinge, Segeltorp, Umeå, and Upplands Väsby starting Nov. 17.

Joakim Oscarsson, the union's Agreement Secretary reportedly said, "When Tesla consistently refuses to sign a collective agreement, it poses a threat to the stability of the Swedish labor market. Everyone who works in Sweden must be covered by Swedish wages and Swedish conditions."

Responding to the development, Tesla reportedly said the workers were already being offered "equivalent or better agreements than those covered by collective bargaining and find no reason to sign any other agreement."

Why It's Important: Sweden is one of Tesla's key markets in Europe and the development comes at a time when the United Auto Workers Union has succeeded in getting Detroit's big three agree to its demand. Reports also suggest Tesla could be UAW's next target and the union has been striving to organize themselves at the former's Fremont California plant.

Battery electric vehicles accounted for 44.4% of the new vehicles sold in Sweden in September, and Tesla's Model is the best-selling vehicle among all the vehicles.

Tesla closed Tuesday's session up 1.33% at $222.18, according to Benzinga Pro data.