Exxon officials have been ordered by a New York judge to explain how the company overlooked a shadow email account used by its former chief executive Rex Tillerson while the company was under subpoena by the New York attorney general's office.

Judge Barry Ostrager ordered Exxon to provide sworn affidavits describing the company's process for identifying and turning over documents. He also demanded an explanation of what documents may have been lost and how that happened.

Ostrager also gave the company until March 31 to surrender documents associated with Tillerson, now serving as secretary of state, and five other members of Exxon's management committee.

The hearing followed the recent disclosure that in addition to his Exxon email, Tillerson had used an alias email account under the name "Wayne Tracker," a probable reference to Tillerson's middle name.

New York Attorney General Eric Schneiderman disclosed the existence of that email as part of its open investigation of Exxon in connection with possible securities fraud over whether the company misled shareholders and the public about climate change.

Tillerson used the Wayne Tracker email account for eight years to discuss climate change-related issues and the risks they posed to the company's business, investigators claim.

The company turned over a handful of the emails in January and explained then that they were overlooked because the company did not have the technical capability to identify them. Exxon now says, however, that locating Tillerson's emails was not one of the priorities originally spelled out by the attorney general.

Those explanations are nothing more than Exxon's "pattern and practice of hiding the ball" in response to the investigation, according to a letter from the attorney general's office filed with the judge prior to the hearing.

"In spite of Exxon's assurances to this Court that it would move 'heaven and earth' to comply with the subpoena, Exxon's conduct outside this Court reflects a pattern of stonewalling and disingenuousness."

New York investigators argued Exxon deliberately delayed the production of the Tillerson records and those of other top managers and that it has failed to confirm that it has preserved all of the records.

Exxon acknowledged it missed a year's worth of Tillerson's Wayne Tracker emails during three searches in 2016 while trying to comply with the subpoena. The Wayne Tracker emails surfaced in a fourth search in January 2017, but the company said it can't find emails from September to November 2014, according to a letter to the judge a day before the hearing.

The company said it focused on turning over records based on the attorney general's original 2015 subpoena that included a prioritized list of documents.

Exxon lawyers argued that the attorney general's "ever-shifting investigative theories" caused the company to first focus on turning over 109,000 documents associated with four employees who studied climate science. Emails from Tillerson and five other management committee members were not a priority, the company said.

"When these documents evidently refuted his investigative theory, the Attorney General informed ExxonMobil that his new 'priority' was documents" from an employee responsible for the preparation of a 2014 report called Energy and Carbon—Managing the Risks and those on ExxonMobil's greenhouse gas issue management team, Exxon's letter said.

Exxon lawyers explained to the judge the company made four exhaustive searches of its files for records in response to the attorney general's request. So far the company has provided a broad sweep of records—2.6 million pages so far—from nearly every corner of the company.

"Despite the Attorney General's assertion that ExxonMobil has not complied in good faith, at no point did ExxonMobil refuse to add a single custodian requested by the Attorney General," according to the letter from Ted Wells, the company's lead attorney.