Visitors to Mather Point at Grand Canyon National Park, Ariz. look out over a rare total cloud inversion. (AP Photo/National Park Service, Erin Whittaker)

The Interior Department’s internal watchdog has opened an investigation into P. Daniel Smith, currently the top-ranking official at the National Park Service, for allegedly making a gesture involving his genitalia in the hallways of the department’s headquarter this year.

Nancy K. DiPaolo, a spokeswoman for Interior’s Office of Inspector General, confirmed late Friday that the office will begin a probe into the allegation. “It’s being processed, and we will be opening an investigation,” she said.

In a letter, an anonymous Park Service employee describes how on either Jan. 10 or Jan. 11, Smith “grabbed his crotch and his penis and acted out as though he was urinating on the wall” while relaying a story to another employee at the Main Interior Building in Washington.

The employee wrote he or she chose not to sign the letter for fear of reprisal from within the Park Service, a division in the sprawling Interior Department. “I wish I could come forward,” the worker wrote, “but retaliation is real.”

The employee added “it could have been a sexual act” but that “regardless, he grabbed his crotch and penis in a public place.”

The March 8 letter was addressed to Interior Secretary Ryan Zinke, whose office forwarded it to the inspector general, DiPaolo said. The Washington Post obtained the letter from the advocacy group Public Employees for Environmental Responsibility, which also received it.

Since taking office, Zinke has pledged to curb a culture of misconduct inside the Park Service, which oversees 417 locations covering more than 84 million acres spread across the United States.

In October, an internal survey revealed more than 1 in 10 Park Service employees felt they had been sexually harassed on the job. Zinke took action by firing four senior management staffers within the department for inappropriate conduct, including sexual harassment.

The agency undertook the survey after a scandal at Grand Canyon National Park, where investigators found that male employees preyed on female colleagues during long trips down the Colorado River.

“I fired four. I will fire 400 if necessary,” Zinke told the Senate Energy and Natural Resources Committee last week.

Zinke encouraged witnesses of improper behavior to come forward: “‘When you see something, say something’ is the policy in the Department of the Interior.”

In early January, the same week of the alleged incident, Smith assumed the role of deputy director at the agency, replacing acting director Michael T. Reynolds after his 300-day term in the temporary position expired. Smith is currently exercising the authority of director for the Park Service because President Trump has not yet named a nominee for that position, which the Senate would need to confirm.

Smith has come under scrutiny from the Office of Inspector General before.

Investigators there determined Smith had improperly helped Washington Redskins owner Daniel Snyder cut down more than 130 trees on park property in 2004 to improve the view of the Potomac River at his Maryland estate. The inspector general’s report said the decision should have been left to biologists at Chesapeake & Ohio Canal National Historical Park.

The Office of Inspector General, which scouts for illegal or inefficient actions within Interior, said it expects the investigation into Smith to be quick. “I wouldn’t expect it to be a long one,” spokeswoman DiPaolo said.

A spokesman for the Park Service did not reply to a request for comment.