TOKYO, March 28 (Reuters) - Shares of Japan's Panasonic Corp fell 6 percent early on Wednesday after the United States began a federal field investigation into last week's fatal crash and vehicle fire of major battery customer Tesla Inc .
Panasonic produces lithium-ion batteries for Tesla in a joint venture with the California-based electric car maker. News of the federal investigation had sent Tesla's shares tumbling more than 8 percent on Tuesday to close at the lowest level in almost a year.
In last week's accident near Mountain View, California, the lithium batteries of the Tesla Model X caught fire, and emergency officials consulted company engineers before determining how to extinguish the battery fire and move the vehicle safely.
(Reporting by Chang-Ran Kim and Minami Funakoshi; Editing by Edwina Gibbs)