Russian flight controllers are working to figure out why a Russian Soyuz capsule carrying three new crewmembers for the International Space Station failed to fire its steering thrusters as planned, officials said on Tuesday.

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NASA astronaut Steven Swanson and cosmonauts Alexander Skvortsov and Oleg Artemyev blasted off aboard a Russian Soyuz rocket at 5:17 p.m. EDT on Tuesday from the Baikonur Cosmodrome in Kazakhstan for what was expected to be a six-hour ride to the station.

The crew’s Soyuz capsule, however, failed to fire its steering rockets as expected, delaying the ship’s arrival until at least Thursday evening.

“The crew is in no danger,” mission commentator Rob Navias said during a NASA Television broadcast.

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The Soyuz has enough supplies for the crew to last beyond two days, should that be necessary, Navias added.

Russian flight controllers were working to figure out if a software issue, a mechanical problem or something else is responsible for the missed thruster burns, added NASA spokesman Josh Byerly.