The security chief for the head of the Environmental Protection Agency worked on the side as a private investigator for the owner of a tabloid news company with close ties to President Donald Trump.

EPA special agent Pasquale "Nino" Perrotta performed regular work for National Enquirer publisher American Media Inc. during the 2016 election, according to person with knowledge of the company's internal workings.

But unlike another private investigator hired by the Enquirer, Perrotta didn't work on such newsroom projects as tracking down sources. Instead, the person told The Associated Press on Tuesday, Perrotta was engaged to discretely handle investigative work at the direction of AMI chairman and CEO David Pecker.

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The person was not authorized to speak publicly about the company's operations and spoke on condition of anonymity. The New York Times first reported Perrotta's link to AMI.

In addition to his job at EPA, Perrotta is the top executive at Sequoia Security Group, a Maryland-based security firm. The person with knowledge of the situation did not know whether Perrotta was paid for his work for AMI and Pecker through Sequoia or another business entity.

A former Secret Service agent, Perrotta has worked at EPA for more than a decade. He was tapped by EPA Administrator Scott Pruitt last year to lead his 20-member, full-time personal protective detail.

Perrotta's predecessor as Pruitt's security chief was reassigned for refusing to acquiesce to the administrator's demands for VIP treatment, including using the emergency lights on a government vehicle to speed through Washington traffic to make airline flights and dinner reservations.

Perrotta did not respond late Tuesday to messages seeking comment. EPA's press office also did not respond to messages seeking comment about the security chief's side business.

AP reported earlier this month that Perrotta oversaw a rapid expansion of Pruitt's security team and the taxpayer-funded precautions used to ensure his personal safety, including the use of first-class airline seats after a fellow traveler cursed at the EPA chief in an airport.

Perrotta also spearheaded the purchase of a $43,000 soundproof booth for Pruitt's office to help ensure his telephone calls could not be overheard by others. The Government Accountability Office found earlier this month that the spending on the pricey privacy booth violated federal purchasing laws.

Democratic lawmakers on Tuesday issued a letter questioning whether Perrotta was improperly operating an outside consulting firm without proper approval from EPA ethics officials.

Under Pecker, American Media became one of the earliest and most fervent backers of Mr. Trump's political career, providing breathless coverage as far back as 2011 to Mr. Trump's promotion of the false theory that President Barack Obama might not be a U.S. citizen.

During the 2016 campaign, Pecker's flagship National Enquirer was in close contact with Mr. Trump's personal attorney Michael Cohen while it attacked Mr. Trump's Republican opponents from its perch in supermarket checkout aisles, printing thin allegations about Sen. Ted Cruz's personal life and alleging Democratic candidate Hillary Clinton was in declining physical and mental health.

AMI also helped Mr. Trump in a far less public fashion. The company paid $150,000 to a former Playboy Playmate for the rights to her story about an alleged affair with Trump during his marriage to Melania, and another $30,000 to a former Trump doorman peddling another story about Trump.

AMI has denied the payments were hush money, though Pecker himself noted in a New Yorker interview last year that the contract with Playmate Karen McDougal prevented her from "bashing Trump."

Records show Perrotta received clearance in March 2013 for limited nongovernment consulting work but was required to get updated approval if his job duties changed. Perrotta received a significant promotion and pay raise last year.

According to the letter approving his work outside the agency, Perrotta told EPA ethics officials he expected to be "self-employed" to provide consulting to two to three clients for approximately three to six hours per week on issues related to cybersecurity and "denial of service insurance."

The 2013 approval, which was in effect for a five-year period that expired last month, also barred Perrotta from using his government position to advance his personal interests.

AP reported in December that EPA paid $3,000 to contractor Edwin Steinmetz Associates last year to search Pruitt's office for secret listening devices. Steinmetz is also listed as a vice president at Perrotta's security firm.

Emails obtained by congressional Democrats showed that Perrotta played a role in the decision to conduct the bug sweep, the contract for which the lawmakers allege he improperly steered to Steinmetz.

Tuesday's letter was signed by Democratic Sens. Tom Carper of Delaware and Sheldon Whitehouse of Rhode Island, who serve on a committee with oversight of EPA. They ask an agency ethics official to re-examine whether Perrotta's outside employment violates agency rules.