This story has been updated with details from an Exxon court filing on June 9.

Up to seven years of emails that former ExxonMobil CEO Rex Tillerson wrote under the alias "Wayne Tracker" may have been erased, a company witness has told investigators for the New York attorney general.

The gap is far longer than the three months Exxon initially reported.

The disclosure came from Connie Feinstein, Exxon's information technology security and consulting manager, who was questioned about Tillerson's secret email alias, created in 2007 under the pseudonym "Wayne Tracker."

During a daylong question-and-answer session related to the attorney general's investigation into whether Exxon mislead investors about climate change, Feinstein explained under oath both how a computer program allowed for the scrubbing of Tillerson's Wayne Tracker emails and the considerable effort the company put in trying to recover them.

A 301-page transcript of the April interview became public last week as part of a batch of documents released by New York Attorney General Eric Schneiderman's office. He lodged them in a state court in support of his claim that Exxon's climate accounting was a "sham" under Tillerson, who is now the U.S. secretary of state.

Feinstein said that a program designed to automatically erase emails from the account's queues after 13 months had never been disabled on the Wayne Tracker account. That opened the possibility that an unknown number of emails may have been erased as far back as 2007.

The Wayne Tracker account was set up without a direct link to Tillerson on Exxon's email servers, giving him a layer of anonymity where he and top executives could address the company's most sensitive business matters, Feinstein said.

It was created at the same time that investigators claim Exxon may have been using two sets of numbers to calculate the cost of carbon emissions as a way to assess climate-related risks to the company's business. One set of numbers was publicly given to investors showing a conservative and less risky calculation; a second, closely held internal "secret" set of numbers painted a less realistic assessment on which Exxon based its business strategy, Schneiderman said in the latest court filings.

Schneiderman has been investigating the company for years, with the first subpoena issued in the fall of 2015, shortly after InsideClimate News and later the Los Angeles Times published separate accounts of Exxon's knowledge of climate risks since the late 1970's. Schneiderman and Massachusetts Attorney General Maura Healey have opened investigations of Exxon under each state's fraud statutes that protect consumers from making investment decisions based on misleading information.

Although neither a company spokesman nor Feinstein responded to requests for comment, Exxon has defend the Wayne Tracker email as "entirely proper" and said there was no attempt by the company to conceal them from investigators.

[In a court brief filed on June 9, attorneys for Exxon wrote: "Seeking controversy and headlines, the attorney general accuses ExxonMobil of destroying documents from purportedly 'key custodians'. The claim is baseless."]

However, Schneiderman has said the existence of the Wayne Tracker account was never reported to his investigators, as it should have been under the subpoena. They discovered references to the account buried in the more than two million pages of documents surrendered by Exxon.

A spokeswoman for Schneiderman declined to comment, saying the documents speak for themselves.

The existence of the shadow email account was disclosed earlier this year by New York investigators who say they have evidence that climate change and the risks it posed to the company's business were discussed by Tillerson and other top executives via the Wayne Tracker account. That information goes to the heart of the attorney general's financial fraud investigation of Exxon.

Exxon admitted earlier this year that emails from Tillerson's Wayne Tracker account had been erased between September and November 2015. But as New York investigators began to press for answers through a series of new subpoenas, the possibility emerged that far more of Tillerson's emails may be missing.

Tillerson's Wayne Tracker account was set up in 2007 so the CEO could have a confidential email address that would be free of the voluminous emails flooding his regular account, including those of activists demanding Exxon change course to more sustainable sources of energy, according to Feinstein's statement.

Feinstein also disclosed that current Exxon CEO Darren Woods has a shadow email under the alias J. E. Gray, though she said it appears that Woods has never used the account.

When Schneiderman's office issued its subpoena in November 2015 seeking records and correspondence going back as far as 1977, Exxon placed a legal hold on all relevant email accounts. But Tillerson's Wayne Tracker account was not included in that hold. Few people in either Exxon's legal or IT departments knew it existed.

The account was not even created under Tillerson's name but in the name of an IT manager at Exxon's corporate headquarters to add a measure of secrecy to the account, making identifying it even more difficult.

"Had it been linked to something that said Mr. Tillerson, then the anonymity would not have been there," Feinstein said.

To prevent old emails from cluttering Exxon's computer system, a program automatically deleted emails more than 13 months old. That program–called a file sweeper–had never been disabled for Tillerson's Wayne Tracker account, Feinstein said.

Because of the overall need to preserve records from top Exxon officials, the sweeper program had been permanently disabled on Tillerson's regular account.

"For Mr. Tillerson, it was disabled, but the Wayne Tracker, there was a mistake and so the file sweeper did not get disabled for the Wayne Tracker account," Feinstein said.

Emails from the Wayne Tracker account from 2007 through 2011 had been created in a company-wide system that was replaced in 2012, Feinstein explained in the interview. The old system did not have an automatic deletion system but all of the emails from that system were incorporated into the new system including Tillerson's alias email, which may then have been swept away.

"The Wayne Tracker account did not have the file sweeper disabled," Feinstein said of the new system.

When asked if emails in the Wayne Tracker account prior to November 2014 were lost to the deletion program, Feinstein said "e-mail before that time would logically have been automatically swept."

Feinstein then qualified her answer by explaining she was not certain that had happened.

Once the attorney general began demanding access to Wayne Tracker emails earlier this year, Feinstein described a herculean effort to try to find them. More than 50 members of the ExxonMobil Information Technology department spent hundreds of hours over 17 days trying to recover the emails, Feinstein said.

The efforts included trying to identify backup systems; looking at Tillerson's laptop, iPhone and iPad; scouring the email accounts of Exxon employees who exchanged emails with Tillerson on his Wayne Tracker account and hiring a forensic data recovery company.

"There were many, many questions asked to just determine if we had exhausted every possibility and looked in every location that we could to try to find this data," Feinstein said during the interview.

She said the oldest backup of Wayne Tracker emails dated back only to Aug. 18, 2015.

It is unclear whether attempts by Exxon to recover the Wayne Tracker emails from secondary sources yielded results.

David Shapiro, a forensic accountant and former FBI agent who specialized in financial crimes, said the missing emails opens Exxon up to questions about whether Tillerson intentionally destroyed sensitive correspondence that he did not want scrutinized outside of a close circle of Exxon confidantes.

"The implication of fraud is heightened," he said.

Allowing the deletion of the emails is merely an irresponsible business practice on one level, but on another it carries the suggestion of outright duplicity by a company that is on its heels over its conduct relative to disclosing climate risks to its investors, said Shapiro, an assistant professor at the John Jay College of Criminal Justice in New York.

"Who knows what's been going on in that secret tunnel," he said.