US auto safety regulators fined Fiat Chrysler Automobiles $70 million Thursday for failing to report key safety data to regulators on death and injury claims linked to their vehicles.

The penalty is an amendment to a July $105 million fine on Fiat Chrysler over its poor handling of auto recalls, taking the total in the enforcement case to at least $140 million and as high as $175 million, said the National Highway Traffic Safety Administration.

The $175 million figure includes $35 million in deferred penalties that will be due if the company fails to abide by the settlement, NHTSA said.

The penalty follows Fiat Chrysler's admission that it failed for years to report key safety data that regulators use to determine if potential defects necessitate a recall.

"Accurate, early-warning reporting is a legal requirement, and it's also part of a manufacturer's obligation to protect the safety of the travelling public," said Transportation Secretary Anthony Foxx.

"We need FCA and other automakers to move toward a stronger, more proactive safety culture, and when they fall short, we will continue to exercise our enforcement authority to set them on the right path."

NHTSA has also ordered a third-party audit to determine the full scope of the reporting failure.

The July fine included a $70 million penalty owed to the NHTSA and $20 million in spending on consumer outreach and incentives to encourage Fiat Chrysler owners to comply with recalls.