Audio of the forceful push led by U.S. Park Police to sweep protesters out of Lafayette Square on June 1, moments before President Trump’s visit to St. John’s Episcopal Church, was not recorded by the Park Police radio communications system, the agency said Tuesday.

The sudden march into the group of protesters, featuring members of the Park Police, Secret Service, D.C. National Guard and Arlington County police, is now under investigation by Congress and the inspectors general of the Interior Department and Justice Department and the subject of civil lawsuits. The sweep along H Street caused an uproar because police used smoke and chemical irritants, along with officers on horseback, to clear out protesters well before a 7 p.m. curfew, with advance announcements that many said they did not hear.

Rep. Raúl M. Grijalva (D-Ariz.), chairman of the House Natural Resources Committee, which is investigating the June 1 incident, said Tuesday that “Trump administration officials ordered the attack on clergy, nonviolent protesters, and working members of the press. For the official audio record of that day to now turn up missing has every appearance of a coverup.”

Grijalva said his committee is hoping to hear from acting U.S. Park Police chief Gregory T. Monahan later this month. “The American people deserve firm, clear answers from the administration,” Grijalva said, “about who issued what orders that day, where those orders ultimately came from, and why these recordings are mysteriously unavailable.”

When investigators review a police operation, they typically rely on audio and video recordings made by police to verify accounts made in statements or interviews. But the Park Police, along with nearly all federal uniformed police, have never worn body cameras. Officers and commanders said they expected that their comments and orders made during the operation would be captured electronically, to create a contemporaneous record of the event.

But that didn’t happen.

“At the conclusion of the demonstrations,” Park Police Lt. Jonathan Hofflinger said in response to an inquiry from The Washington Post, “we discovered that the radio recorder was not working and did not record any transmissions. However, written radio logs were generated as a redundant practice. This recorder issue has since been rectified.”

Hofflinger did not respond to questions about how written radio logs were compiled, why the recorder didn’t work or how it has been rectified. Monahan did not respond to requests for comment. It was unclear whether the Park Police communication system has failed to record transmissions in other instances.

“It’s very disappointing,” said Kenneth Spencer, chairman of the Park Police’s Fraternal Order of Police Labor Committee. “It’s frustrating, especially at the officer level, because a lot of information that would serve the perspective of the officers on what was actually taking place would have been recorded.”

Spencer feels that Park Police officers responded appropriately to the situation and that his command staff gave proper direction. “Myself included,” Spencer said, “there were many officers expressing what kind of objects they were being hit with, where it was coming from. Everything of that nature was being expressed on the radio.”

Spencer offered support for Monahan’s statement that the Park Police did not use tear gas that evening. “When we were getting ready to deploy to H Street on June 1,” Spencer said, “it was right on the radio transmissions that ‘CS gas is not authorized and everybody remove your gas mask.’ We did remove our masks, and we didn’t use CS gas. That was one of the things that didn’t get recorded.”

Monahan has acknowledged that Park Police used smoke canisters and pepper balls containing an irritant powder.

The “written radio logs” Hofflinger mentioned are handwritten notes taken by dispatchers, Spencer said, and then given to an officer to type into Excel spreadsheets. The notes say who was speaking and what they were describing in their transmissions, Spencer said. He did not know if the notes were taken because commanders knew the recording system wasn’t working, or as a standard backup. But he did say the Park Police radio system “has been a problem for decades. We have brought it to the attention of our command staff and the National Park Service” with repeated complaints.

Monahan had been scheduled to testify before a House Natural Resources Committee hearing on the incident last week but declined to appear. A letter from an Interior Department official said Monahan could not attend the hearing because the Park Police was still “in its highest operational status” due to protests at parks in Washington.

“These are things that are just inexcusable in 2020,” said Geoff Alpert, a criminologist at the University of South Carolina who has studied how police recall critical incidents in subsequent interviews. He and others said having an audio record of an incident is crucial.

“It is the investigation,” Alpert said. “It’s all you’ve got. Memory and reasoning can be clouded. They can be manufactured. A recording of an action is far more preferred than trying to get someone to remember what they did and why.”

Steve Souder, a widely respected public safety communications expert who oversaw 911 systems in Arlington, Montgomery and Fairfax counties, said of the Park Police failure, “I find it quite shocking. They want this stuff recorded. They have nothing to hide.”

Souder said modern dispatch technology has made it easy to record every transmission, by dispatchers, commanders and officers in the field, even on systems with multiple channels or talk groups.

“In my mind, you should record everything,” Souder said. “You never know when you’re going to need it.” He said that “these recording systems are all digitized. They record everything.”

Spencer said there is some video of the operation taken by authorities that has not been released. He said video of the “large chaotic event” would show provocative actions by the protesters, such as throwing large objects or shooting fireworks at the police, which protesters have largely denied. But even those cameras would capture only select areas of the protest, and not the full sweep of interactions being reported by officers over the radio.

The incident, which started about 30 minutes before an announced curfew, sparked criticism because protesters were forced from the area amid smoke and chaos, and because the president showed up soon after for a photo op in front of the church.