Mounting losses and an analyst downgrade pushed down shares of U.S. Auto Parts Networks more than 20 percent Wednesday morning.

After the market closed Tuesday, the Carson company, an online seller of automotive parts and accessories, reported a third-quarter loss of $5.3 million or 17 cents a share, compared with a net loss of $13 million or 43 cents a share for the same period last year. The most recent quarterly loss included $5.5 million in costs related to the company’s acquisition of JC Whitney, a former competitor in the car parts market.

After the results were announced, analyst Mitchell Bartlett at Craig Hallum downgraded the company’s stock to “hold” from “buy.” Bartlett lowered his 12-month target price to $6 a share from $11.

Chief Executive Shane Evangelist said in a statement that the JC Whitney acquisition was a major transition during the quarter and now the company can “look forward to reversing negative trends in that business that occurred while we were focused on completing the integration.”

By mid-day, shares of U.S. Auto Parts traded at $3.92, a loss of $1.18 or 23 percent compared to its Tuesday close.