Shares of Carvana Co. fell nearly 5% late Monday after the company, which operates a platform for buying used cars online, said it wants to sell 6 million shares in a follow-on offer. Additionally, certain stockholders are proposing to sell 4 million shares, and a selling stockholder has granted the underwriters the right to buy up to 1.5 million shares, the company said. Wells Fargo, Citigroup, and Deutsche Bank are the book runners. In a separate press release, Carvana released preliminary results for its first quarter, saying it expects to have sold about 18,450 vehicles, compared with 8,334 sold in the first quarter of 2017. The increase in retail cars sold "was driven in part by increased penetration in existing markets, as well as Carvana's business participating in 56 markets as of March 31, 2018 from 23 markets as of March 31, 2017," the company said in the statement. Net sales and operating revenues are to be about $360 million, compared with $159.1 million for the year-ago period, Carvana said. Analysts polled by FactSet expect about 18,000 vehicles sold and sales around $343 million in the quarter. Carvana shares ended the regular trading session up 2%.