Construction at the White House may have contributed to an incident this month in which the president’s helicopter came dangerously close to a commercial jet over Washington, according to a new report from the National Transportation Safety Board.

According to the report, work to build a new ballroom at the White House forced officials to move the helicopter’s takeoff location temporarily from the South Lawn to the Ellipse, the park south of the White House. But the new location may have been less optimal for communicating with air traffic controllers, leading to communication glitches, the report said.

Technicians “conducted a coverage analysis and determined that there was not adequate line-of-sight to ensure communications” between the Ellipse and the tower ”while construction was ongoing at the White House,” the board’s report reads. There had been no known issues with the radio frequency before the incident.

The report chronicled how garbled communications caused the airport controller to miss multiple warnings from the helicopter crew that they were minutes from takeoff — a notification that would have signaled to the controller to temporarily ground planes while the helicopter passed through the area. Instead, the controller allowed an Envoy Air jet bound for Pensacola, Fla., to depart from an airport runway just as Marine One was about to take off, resulting in the plane and the helicopter passing each other less than a mile apart.

The board’s findings are preliminary, and its investigation of the incident is ongoing.

The White House grounds have been the site of extensive construction, as crews work 20 hours a day, seven days a week, to make progress on Mr. Trump’s plans to build a massive ballroom. The project has been hotly contested, but last week, the Supreme Court temporarily allowed Mr. Trump to forge ahead while it considered whether the 90,000-square-foot project can be completed.

Representatives for the White House did not address questions about the role that the White House ballroom construction may have played in the incident.

“Marine One flights are piloted by the finest aviators in the world, and the White House maintains the utmost confidence in these patriots and other security officials who are responsible for ensuring the president’s safety,” Kush Desai, a spokesman for the White House, said in a statement. “Although the president was at no point in harm’s way during the Aug. 4 momentary loss of separation, the White House continues to work with relevant military, F.A.A., and other security personnel to ensure the president’s continued safety.”

Under current procedures, controllers are expected to keep the congested skies around National Airport clear of traffic when the president’s helicopter is traversing the area.

In the wake of the Aug. 4 incident, Sean Duffy, the transportation secretary, said that the president was never in any danger because the two aircraft’s flight paths would not have converged. He blamed the incident on faulty telecom issues, and earlier this week, Bryan Bedford, who leads the Federal Aviation Administration, told reporters that his agency had made changes to communication procedures and relocated an air traffic antenna to help fix the problems.

“The F.A.A. took immediate action following the Aug. 4 incident involving Marine One,” Hannah Walden, a spokeswoman for the Federal Aviation Administration, said in a statement, listing the changes that Mr. Bedford had referenced earlier in the week.

But the event nonetheless harked back to last year’s tragic collision over National Airport, in which a passenger jet and an Army Black Hawk helicopter collided in midair, killing 67. That accident focused national scrutiny on longstanding shortfalls in air traffic control staffing, and revealed that senior F.A.A. officials had ignored years of warnings that crisscrossing flight paths through the skies surrounding the airport posed critical safety risks.

In the months that followed, the F.A.A. took steps to reroute helicopter flight paths through the area, allowing only the most important government rotorcraft — such as Marine One — to traverse the airspace, and only when other flight traffic was grounded. The agency also ended the practice of visual separation, by which overtaxed controllers left helicopter pilots on their own to “see and avoid” oncoming airplane traffic, near busy airports like Ronald Reagan National Airport.

But critics, including most of the families of the victims of last year’s fatal crash, say the moves are not enough to avoid a repeat of a similar disaster.

The victims’ families have lobbied for new laws to force the F.A.A. to require that all aircraft be equipped with advanced technology that would allow pilots to track real-time location signals from other aircraft, arguing that would reduce their reliance on air traffic controllers to alert them to potential collision risks. An N.T.S.B. report into last year’s crash determined that if the airplane and helicopter had been equipped with such technology, the pilots would have had almost a minute’s forewarning that they were on a collision course, giving them ample time to avoid each other.

Efforts to enact such legislation, however, have been gridlocked for months as lawmakers in the House and Senate bicker over two competing approaches, which differ over what airplanes would be required to carry such technology and how strictly the military would be curtailed, statutorily, from turning off its location-broadcasting equipment when flying through restricted airspace.