The U.S. Federal Aviation Administration on Monday said SpaceX must investigate why the second stage of its workhorse Falcon 9 rocket malfunctioned after a NASA astronaut mission on Saturday, grounding the rocket for the third time in three months.

The Federal Aviation Administration confirmed it had grounded SpaceX’s Falcon 9 rocket pending an investigation into why the rocket’s second stage missed its deorbit landing target zone after this weekend’s Crew-9 launch from Cape Canaveral,

The malfunction caused the Falcon 9 booster to fall into an area of the Pacific Ocean outside the designated safety zone approved by the FAA for the mission.