"Search and rescue teams report they are in contact with the Soyuz crew, who report they are in good condition", Nasa wrote on Twitter.
Gerst tweeted his relief that the two astronauts were safe, saying the day's events "showed again what an wonderful vehicle the Soyuz is, to be able to save the crew from such a failure".
All Russian manned space launches have been suspended after the incident, according to Russia's RIA news agency.
"NASA Administrator Jim Bridenstine and the NASA team are monitoring the situation carefully", said NASA, in a statement released early Thursday.
Russian Federation has set up a state commission to investigate the Soyuz booster rocket failure.
"The Soyuz capsule is returning to Earth via a ballistic descent, which is a sharper angle of landing compared to normal".
While the Soyuz rocket is considered a reliable launch vehicle in the space sector, this is not the first failure in the Soyuz program's history.
Dmitry Peskov, the Kremlin's spokesman, put it more bluntly in his daily conference call with journalists: "Thank God everyone is alive". The first crewed flights would not take place until several months after that, unless the space agency is willing to take additional risks with those missions.
Thursday's mishap occurred as the first and second stages of the Russian rocket separated shortly after the launch from Kazakhstan's Soviet-era Baikonur cosmodrome. "We are thrilled that, even though it was a launch failure, all of the safety systems worked".
The Russian Soyuz spacecraft is now the only vehicle for ferrying crews to the International Space Station following the retirement of the US space shuttle fleet.
The astronauts were to dock at the International Space Station six hours after the launch and join an American, a Russian and a German now aboard the station.
The Russian Soyuz spacecraft is now the only vehicle for ferrying crews to the International Space Station following the retirement of the USA space shuttle fleet. But Peggy Whitson, a retired NASA astronaut who survived a ballistic re-entry in a Soyuz capsule in 2008, described the experience as a harrowing one in an interview with The Houston Chronicle later that year.
"As we wait for the conclusions of a Russian probe, the Soyuz will perhaps be grounded for some time", he told AFP.
Russian space chief Dmitry Rogozin said he was forming a state commission to investigate what caused the failure. The Russian space agency also sent 70 rocket engines back to production lines in 2016 to replace broken parts. Instead, the two astronauts landed safely a half-hour later, rescued by the capsule's "automated abort systems" that "is created to be effective", said Kenny Todd, the International Space Station manager. He didn't say if he suspected any of the current crew of three Americans, two Russians and a German aboard the station of malfeasance.