“The cause of the failure was a gradual deterioration of the Zefiro 40’s nozzle,” the European Space Agency said.

The Zefiro 40 second stage, made by Italian aerospace company Avio, suffered “an unexpected thermomechanical over-erosion” of a carbon component purchased in Ukraine, it said.

Arianespace’s Pierre-Yves Tissier said the conclusion was based on an examination of identical parts and had yet to be confirmed through further testing.

ESA added that “no weakness in the design of the Zefiro 40 has been revealed during the investigation.”

The launch was the third failure in the past eight launches of Vega and Vega C rockets, an embarrassment to the agency and its partners.

“We will overcome this very difficult moment,” Arianespace head Stephane Israel told reporters.

ESA Chief Josef Aschbacher added that measures will now be taken “to emerge stronger from this crisis”.

The launch was intended to carry two Airbus Earth observation satellites, Pleiades Neo 5 and 6, into orbit. The satellites would have been part of a constellation capable of taking images of any point on the globe at a resolution of 30 centimeters (12 inches).