(Bloomberg) -- The US Commerce Department on Wednesday opened an investigation into allegations that solar cells and panels imported from four Southeast Asian countries are being unfairly subsidized and priced below their production costs. 

Companies making solar equipment in the US — including Convalt Energy Inc., First Solar Inc., Hanwha Qcells USA Inc. and Mission Solar Energy LLC — formally sought the probe last month, saying tariffs are needed to counteract unfair practices by rivals in Cambodia, Malaysia, Thailand and Vietnam. The case will play out against the backdrop of a presidential campaign, with both incumbent Democrat Joe Biden and his presumptive Republican challenger, Donald Trump, casting themselves as defenders of US manufacturing.

First Solar shares jumped on the news, rising almost 5% before giving up some of their gains. Shares were trading at $192.42 at 1:18 p.m. Eastern Time. 

The investigation will proceed on parallel tracks, with the Commerce Department assessing whether dumping or subsidizing is happening — and, if so, the margin of dumping or the amount of the subsidy. The International Trade Commission, meanwhile, is set to determine whether there is material injury or threat of material injury to the domestic industry as a result. The commission opened an initial public meeting on the matter Wednesday morning.

Depending on the initial findings, importers could be forced to make cash deposits on affected imports based on estimated duties as soon as four months from now.  

Read More: US Power Developer Warns New Trade Probe Imperils Solar Push

Some renewable developers and foreign manufacturers opposed opening the investigation. NextEra Energy Inc. urged the Commerce Department to reject the petitions as having been improperly filed. Canadian Solar Inc. said the companies pursuing the claim hadn’t shown sufficient industry support. And Illuminate USA LLC, the manufacturing joint venture from Invenergy LLC and LONGi Green Energy Technology Co., stressed that while the probe targets crystalline silicon solar cells, there is no US production of that equipment today.

(Adds First Solar share price reaction in the third paragraph.)

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