The second stage of a SpaceX Falcon 9 rocket sustained a rare but catastrophic failure Thursday night, disintegrating in orbit during the deployment of the company’s latest batch of Starlink internet satellites.

In a posting on X two hours after launch, Elon Musk, the chief executive of SpaceX, reported that the rocket had suffered a “RUD” — rapid unscheduled disassembly — while in orbit. “Team is reviewing data tonight to understand root cause,” he wrote.

It remained uncertain whether SpaceX could salvage the 20 Starlink satellites jeopardized by the rocket malfunction.

This is the first failure of a Falcon 9 rocket since 2016, when one exploded on the launchpad during the loading of propellants for an engine firing test. Between that explosion, which destroyed an Israeli satellite, and the malfunction on Thursday, SpaceX had enjoyed a streak of more than 300 successful Falcon 9 missions.

The failure will most likely slow the rapid pace of Falcon 9 launches — one every 2.8 days so far this year. Company officials have said they were aiming to launch more than 140 times this year, up from 91 Falcon 9 launches last year.

It could also delay upcoming missions taking astronauts to orbit. The private Polaris Dawn mission led by the entrepreneur Jared Isaacman is scheduled for the end of this month. And in mid-August, Crew-9 for NASA is expected to take four astronauts to the International Space Station.