WEST BATON ROUGE PARISH, La. (BRPROUD) – The Federal Aviation Administration updated the cause of the fatal Sunday helicopter crash to unknown.

The updated preliminary report now says the helicopter “crashed under unknown circumstances.” The FAA initially said the Robinson R44 helicopter’s tail rotor hit a tree before crashing into a field on Sunday, March 26.

Two Baton Rouge police officers were killed in the crash. They were identified by BRPD as Sgt. David Poirrier, 47, and Cpl. Scotty Canezaro, 38. After the deadly crash, the Baton Rouge Police Department placed a moratorium on helicopter use on Tuesday.

The National Transportation Safety Board said the crash happened at 2:39 a.m. 10 miles away from Baton Rouge. Investigators are looking into three broad areas — the pilot, the operating environment and the aircraft itself. The investigation could take 12 to 24 months.

Several agencies are investigating the crash.