Investigators are asking residents near Charlottesville, Virginia, to “not discard any unusual objects or debris” found in or near their property as they search for causes of the fatal Aug. 12 crash of a Virginia State Police Bell Helicopter 407.

Two Virginia State Police pilots were killed in the crash, which occurred as they were supporting police on the ground monitoring violent protests in Charlottesville.

The investigation by the NTSB and state police into the crash is ongoing and “involves actual reconstruction of the helicopter to aid NTSB investigators with identifying the exact cause,” the state police said. Those agencies conducted an extensive examination and search in and around the crash site, just west of Charlottesville in Albemarle County.

“However, investigators are asking residents within that area to not discard any unusual objects or debris – no matter how large or small – found in or around their property,” the troopers said.

An NTSB official told R&WI that investigators have recovered all of the 407’s major components, “but because of the fragmentation that occurred during the accident sequence, it’s possible that there may still be small pieces of wreckage from helicopter in the area.” The safety board expects to publish a preliminary accident report later this week.

According to the NTSB, the aircraft was not equipped with a flight data recorder or cockpit voice recorder, nor was it required to be. In an update, the board said the 407’s tail boom was lodged in a tree about 100 yards from the main wreckage, which was damaged in a post-crash fire.