U.S. regulators said on Friday they were reviewing claims that Tesla Inc should have recalled 2,000 of its electric cars in May instead of issuing a software upgrade to fix a potential defect that could have resulted in battery fires.

Axar.az reports citing Reuters that the U.S. National Highway Traffic Safety Administration (NHTSA) said it opened a review to evaluate claims made in a defect petition about Tesla’s handling of the software upgrade in 2,000 Model S and Model X vehicles from the 2012-2019 model years.

Tech entrepreneur Elon Musk’s Tesla has also been sued over updates to its battery charging software and this week faced complaints involving vehicles that crashed in parking lots while using a self-driving feature.

The 2,000 vehicles covered by the defect petition to NHTSA received a battery management software upgrade in May in response to a potential flaw that could trigger non-crash-related fires. The petition was filed Sept. 17 by the offices' lawyer Edward C. Chen on behalf of Tesla owners.

It said the software update was believed to have reduced the driving range of the affected vehicles by 25 miles or more per charge.

Tesla shares dropped about 2% from the session high on Friday but recovered slightly to close down 0.7% at $231.43.