Elon Musk, the CEO of SpaceX, suspects a 2-foot steel strut snapped inside its Falcon 9 rocket and led to last month's explosion shortly after liftoff at Cape Canaveral.

Musk told reporters during a Monday briefing that they are looking at a flawed strut in the second stage liquid oxygen tank, which was holding a helium tank.

Musk said the struts had flown many times before without any problem. He said there are hundreds of struts on each rocket, and they are tested to withstand 10,000 pounds of force. However, two minutes into the June 28 launch, one of the struts in the second stage of the unmanned Falcon 9 rocket likely broke loose at only 2,000 pounds of force.

Musk said the strut was from a supplier, which signed off on its certification.

SpaceX will no longer user those particular struts, Musk said.

He explained the impact of the break likely led the helium bottles inside to snap, releasing the helium and causing an overpressure in the stage. That led to the destruction of the rocket and forced the Dragon capsule that was headed for the International Space Station to crash into the ocean.

More than 5,200 pounds of space station cargo were on board the rocket, including the first docking port designed for future commercial crew capsules, a new spacesuit and a water filtration system. Student experiments and research were also lost with the cargo.

Musk stressed at the news conference that these are preliminary results. He indicated future components will need to be re-certified.

"Most of the people who are with the company today have only seen success," Musk said, "and not seen failure quite as much."

The SpaceX team will be sending a remote submersible vehicle to the debris area in the ocean to see if more pieces are recoverable. The next Dragon capsule flight will have software added that will deploy parachutes if another emergency happens.

Musk said the setback should only cause a few months delay in their next launch, which is set for September.

Information from The Associated Press was used in this report.

Here is a video still sequence of the launch failure: