SpaceX CEO Elon Musk says he has a better idea about what happened during last month’s Falcon 9 explosion.

The rocket exploded about 2 minutes after liftoff from Cape Canaveral late last month.

Musk said the problem stemmed from a faulty strut inside the rocket’s upper stage. The strut’s failure caused an increase in helium gas which caused the upper stage of the Falcon 9 to explode.

While Musk says they think they’ve gotten to the bottom if this problem, his engineers are using this an opportunity to double check other systems:

“We’re looking very closely– just in general – is there anything we can do to reduce the probability of failure in future flights,” said Musk.

SpaceX will replace the strut with a stronger material. Musk said SpaceX launches will be delayed until at least September.