In an anomaly update Friday, SpaceX said the investigation into the Sept. 1 explosion that destroyed a Falcon 9 rocket has narrowed down the fault to “to one of the three composite overwrapped pressure vessels (COPVs) inside the LOX (liquid oxygen) tank.” The Elon Musk-owned company also reiterated its intent to return “to flight before the end of the year.”

The investigation into the incident is being conducted by SpaceX with help from NASA, the U.S. Air Force, the Federal Aviation Administration and other industry experts. According to the update, the investigation has worked through a fault tree to methodically arrive at likely causes for the accident.

After testing at the company’s facility in McGregor, Texas, it “has shown that it can re-create a COPV failure entirely through helium loading conditions. These conditions are mainly affected by the temperature and pressure of the helium being loaded.”

SpaceX still doesn’t know the exact cause behind the breach in the cryogenic helium system, and establishing that is one of the two focus areas for the company now. The other is to develop “improved helium loading conditions that allow SpaceX to reliably load Falcon 9.”

The launch site where the accident took place, LC-40 in Cape Canaveral, Florida, suffered a lot of damage and is not presently usable. But while announcing its intent to return to flight in 2016, SpaceX said: “Our launch sites at Kennedy Space Center, Florida, and Vandenberg Air Force Base, California, remain on track to be operational in this timeframe.”

The Falcon 9 rocket that blew up was still at the launch pad at the time of the incident and was being prepared for flight. It was a commercial flight that was carrying an AMOS-6 communications satellite for a Spacecom, an Israeli company.