(Reuters) — The U.S. Securities and Exchange Commission has opened an investigation into Tesla Inc. over a whistleblower complaint that the company failed to properly notify its shareholders and the public of fire risks associated with solar panel system defects over several years, according to a letter from the agency.

The probe raises regulatory pressure on the world's most valuable automaker, which already faces a federal safety probe into accidents involving its driver assistant systems. Concerns about fires from Tesla solar systems have been published previously, but this is the first report of the investigation by the securities regulator.

The SEC disclosed the Tesla probe in response to a Freedom of Information Act request by Steven Henkes, a former Tesla field quality manager, who filed a whistleblower complaint on the solar systems in 2019 and asked the agency for information about the report.

"We have confirmed with Division of Enforcement staff that the investigation from which you seek records is still active and ongoing," the SEC said in a Sept. 24 response to Mr. Henkes, declining his request to provide its records. The SEC said the letter should not be taken as an indication by the agency that violations of law had occurred. Reuters was able to confirm the response.

Mr. Henkes, a former Toyota Motor quality division manager, was fired from Tesla in August 2020 and he sued Tesla claiming the dismissal was in retaliation for raising safety concerns. Tesla did not respond to Reuters' emailed questions, while the SEC declined to comment.

In the SEC complaint, Mr. Henkes said Tesla and SolarCity, which it acquired in 2016, did not disclose its “liability and exposure to property damage, risk of injury of users, fire etc. to shareholders” prior and after the acquisition.

Tesla also failed to notify its customers that defective electrical connectors could lead to fires, according to the complaint.

Tesla told consumers that it needed to conduct maintenance on the solar panel system to avoid a failure that could shut down the system. It did not warn of fire risks, offer temporary shutdown to mitigate risk, or report the problems to regulators, Mr. Henkes said.

More than 60,000 residential customers in the U.S. and 500 government and commercial accounts were affected by the issue, according to his lawsuit filed in November last year against Tesla Energy over wrongful termination.

It is not clear how many of those remain after Tesla's remediation program.