Tesla said on Tuesday that the Justice Department had requested documents from the company after its chief executive, Elon Musk, abruptly announced that he had lined up funding to convert the publicly traded electric-car maker into a private company.

The request for information suggests that the Justice Department has opened a preliminary investigation into Mr. Musk’s market-moving Twitter post on Aug. 7 about the potential buyout.

The Justice Department inquiry, along with an intensifying Securities and Exchange Commission investigation into Tesla’s practices and communications, substantially increases the risks facing the embattled company. Tesla already is under intense financial pressure, with its shares down 25 percent since early August, and the government investigations introduce the possibility of costly penalties or other sanctions.

Tesla said in its statement on Tuesday that it received the Justice Department’s request last month and “has been cooperative in responding to it.” The company released the statement after Bloomberg News reported that federal prosecutors had begun an investigation.