In a series of tweets this morning, SpaceX founder and CEO Elon Musk provided a brief update of the company’s investigation into the explosion last week that destroyed a Falcon 9 rocket and the Amos-6 communications satellite during a pre-launch test. The cause remains unknown.

Musk (@elonmusk) called it “the most difficult and complex failure we have ever had in 14 years,” noting that it happened “during a routine filling operation” when “engines were not on and there was no apparent heat source.” He offered appreciation to NASA, the FAA, the Air Force “and others” for “support & advice.”

He said they are “Particularly trying to understand the quieter bang sound a few seconds before the fireball goes off” that “May come from rocket or something else.” He asked anyone with recordings of the event to email them to report@spacex.com.

In reply to someone else, he said SpaceX has not ruled out the possibility that something hit the rocket.

A video of the September 1 incident posted by USLaunchreport.com shows an eruption in the area of the second stage, with fire quickly engulfing the entire vehicle followed by a series of explosions and the Amos-6 satellite inside its shroud falling to the ground and itself exploding.

Today’s tweets are the only information SpaceX has made available since a statement released last Friday, a day after the “anomaly.” SpaceX itself is in charge of the investigation. It was a commercial launch of a commercial satellite and therefore regulated by the FAA’s Office of Commercial Space Transportation. Under those regulations, the relevant company leads the investigation, not the government.

This event took place during a routine pre-launch “static fire” test two days before the scheduled launch from Space Launch Complex-40 (SLC-40) at Cape Canaveral Air Force Station, FL. SpaceX leases the pad from the Air Force. The video suggests that the pad suffered extensive damage. SpaceX has not explicitly stated how much damage was incurred, but in last week’s statement noted that it is the final stages of preparing another launch pad at NASA’s adjacent Kennedy Space Center. SpaceX leases NASA’s Launch Complex 39A (LC-39A), a launch pad once used for Apollo and space shuttle launches. Both the Falcon 9 and the new Falcon Heavy rocket SpaceX is developing can be launched from LC-39A. SpaceX also leases another Air Force launch pad at Vandenberg Air Force Base for launches into polar orbits and is building its own launch site near Brownsville, TX. It therefore has options beyond simply repairing SLC-40, which likely will be expensive and time consuming.

SpaceX has a full manifest of commercial and government launches that were planned for this year and beyond, including cargo missions to the International Space Station (ISS) for NASA and the first flights of its new Falcon Heavy. It is not clear at this point when any of those launches will take place.

The Amos-6 communications satellite destroyed in the incident was owned by Israel’s Spacecom and built by Israel Aerospace Industries. Facebook planned to use most of the satellite’s capacity to provide Internet service to African countries. The satellite was covered by two insurance policies, one for the period of time before launch (transport and pre-launch preparations) and another beginning with launch. Since this happened during a pre-launch test, the former policy was in effect. Press reports in the Israeli media quote Spacecom officials as saying they expect to recover $205 million from insurance as well as either $50 million from SpaceX or a future launch at no cost.