With the federal government opening a formal investigation into the safety of Tesla Model S battery systems, CEO Elon Musk is questioning why the electric car is being scrutinized.

Musk took to Twitter on Tuesday: @elonmusk:"Why does a Tesla fire w/ no injury get more media headlines than 100,000 gas car fires that kill 100s of people per year?" @elonmusk: What makes this incredibly unjust is that the Model S to date has the best safety record of any car on the road (no injuries or deaths ever)

Tesla CEO Elon Musk at the 2013 New York Times DealBook Conference Getty Images

The tweets are the latest public comment from Musk defending the safety of the Model S.

At The New York Times Dealbook Conference last week, he was asked about the Model S inquiry and didn't hesitate to proclaim that the popular electric car would not be recalled. (Read more: Regulators open probe into Tesla following Model S fires)

"There is definitely not going to be a recall," Musk said last Tuesday. "There is no reason for a recall. ... The perception is, if you read the headlines, that Teslas have a greater propensity to catch fire than other cars, and actually nothing can be further from the truth."