The flight of China’s latest heavy-lift carrier rocket, the Long March 5-Y2, failed on Sunday evening when an anomaly occurred after its 7:23 pm blastoff from Wenchang Space Launch Center in Hainan province.

Experts are working to discover exactly what happened.

The Long March 5, China’s largest rocket to date, made its maiden flight in November, sending its payload into a preset orbit. The Y2 designation of Sunday’s rocket signifies the second in the series.