Elon Musk says rocket explosion is the most “difficult and complex” failure SpaceX has ever had

An explosion on the launch site of a SpaceX Falcon 9 rocket at Cape Canaveral, Fla. (U.S. Launch Report/Handout via Reuters)

Since it was founded in 2002, SpaceX has had its share of failures. Its first three rockets blew up, nearly bankrupting the company. Then last year, another exploded a couple minutes into its flight to deliver more than $100 million worth of cargo to the International Space Station.

But the loss of a rocket last week is “turning out to be the most difficult and complex failure we have ever had in 14 years,” Musk said on Twitter early Friday. SpaceX is leading the investigation into what caused its Falcon 9 rocket to explode as it stood on a launch pad at Cape Canaveral Air Force Station last week as it was being fueled in preparation of a test firing of its engines.

Musk tweeted Friday that it was a “routine filling operation. Engines were not on and there was no apparent heat source.” He said a focus of the probe was “trying to understand the quieter bang sound a few seconds before the fireball goes off. May come from rocket or something else.”

He asked the public to email any recordings of the event to the company. And he also said that he could not rule out that the rocket ignited after something hit it.

The Federal Aviation Administration, NASA and the Air Force are aiding in the investigation. Here are his tweets: