Tesla reported a 13% drop in first-quarter auto sales on Wednesday, April 2, amid lower production during factory upgrades and blowback over CEO Elon Musk's work for the Donald Trump administration. The news also came as a warning that the company’s first-quarter earnings report, due later this month, could disappoint investors.

Musk's electric vehicle company delivered 336,681 units in the quarter ending March 31, under analyst expectations and down from sales of 387,000 in the same period a year ago, as it pointed to the "loss of several weeks of production" while it ramps up upgrades for its Model Y output.

Tesla’s stock has plunged by roughly half since hitting a mid-December record, as expectations of a lighter regulatory touch and big profits with Trump as president were replaced by fear that the boycott of Musk's cars and other problems could hit the company hard.

Analysts are still not sure exactly how much the fall in sales is due to the protests or other factors. Electric car sales have been sluggish in general, and Tesla, in particular, is suffering as car buyers hold off from buying its bestselling Model Y because of plans for an updated version later this year.