US regulators have ended a two-year investigation into how Exxon Mobil accounted for oil and gas prices and the risks climate change posed to its business, the company said Friday.

The US Securities and Exchange Commission told Exxon in a letter on Thursday it had closed the case and would not recommend penalties against the oil company.

"We are confident our financial reporting meets all legal and accounting requirements," Exxon Mobil spokesman Scott Silvestri said in a statement.

He said the company cooperated fully with the inquiry, "ultimately producing more than 4.2 million pages of documents."

Under US securities law, companies must inform investors of material risks to their business.

According to press reports, the probe had focused on how the company accounted for future costs in complying with regulations meant to curb greenhouse gas emissions and how it valued oil and gas assets.

The SEC opened the investigation in January 2016, at a time when many companies had cut estimated asset values.

Exxon Mobil cut its proved oil reserves by three billion barrels to 20 billion barrels at the end of 2016 due to falling prices, saying it was a necessary step to meet SEC accounting requirements.