Investors betting against Elon Musk's electric-auto maker Tesla collectively lost more than $1.5 billion on Thursday as the company's stock rocketed higher after its better-than-expected earnings report.

Tesla finished Thursday's session up 10.3% at $640.81 per share, meaning short sellers betting against the stock lost in excess of $1.5 billion in mark-to-market losses on the day, according to data firm S3 Analytics.

In fact, Tesla short sellers are now down more than $5.2 billion this year in mark-to-market losses after losing $2.89 billion in 2019, S3 said. Since the stock's low of $178.97 on June 3, 2019, Tesla short sellers have covered 19.11 million shares, worth $11.1 billion, and are down $12.43 billion in mark-to-market losses, according to S3's Ihor Dusaniwsky.

"Shorts were trampled by a Tesla Semi as its stock price rose +9% within the first 5 minutes of trading and had little chance to close out positions at anywhere near yesterday's closing price," he said in a note. "Tesla's short squeeze will probably shift into a higher gear as some short sellers re-evaluate their short thesis and begin to trim or close out their short exposure."

The spike in Tesla shares came after the company reported fourth-quarter earnings of $2.14 per share, well ahead of expectations for $1.72 per share. It said it expected positive cash flow and net income on a continuing basis going forward barring one-time production investments, a relief to those who'd poured cash into the young auto company in recent years.