The stock price for electric truck company Rivian fell below the price of its initial public offering after Amazon said it would also buy electric delivery vans from Chrysler owner Stellantis.

Amazon is Rivian’s second-largest shareholder, and a deal to buy 100,000 electric vans from the start-up formed one of the cornerstones of the company’s appeal during its soaring IPO in November.

But on Wednesday, Stellantis announced a deal to sell its own electric Ram ProMaster vans to the online shopping company from 2023.

Competition among carmakers is heating up in electric commercial vehicles: General Motors unveiled its battery-powered Chevrolet Silverado on

Wednesday, a work truck starting at $40,000 and meant to challenge Ford’s F150 Lightning electric pick-up. Ford said on Tuesday that it would increase production of the Lightning to satisfy strong consumer demand.

Carlos Tavares, Stellantis chief executive, described estimates that the deal with Amazon would lead to “tens of thousands” of van sales as “extremely conservative” — raising the prospect that the order rivals the size of Rivian’s deal with Amazon.

The vehicles would “have specific features that will be focused on enhancing the performance of last-mile delivery”, Tavares told the Financial Times.

Rivian’s stock fell as much as 16 percent to $75.13 on Thursday, below its IPO price of $78 a share. The shares recovered, but still ended the day 3 percent lower at $87-33

The California-based company had surged as high as $179-47 within days of its November 10 listing, with a torrent of options trading associated with its stock. At one point the lossmaking group had a market valuation higher than

Volkswagen, Ford and General Motors.