“Superficial fissures have been found in some places on the Zarya module,” Vladimir Solovyov, chief engineer of rocket and space corporation Energia, told RIA news agency. “This is bad and suggests that the fissures will begin to spread over time.”

He did not say if the cracks had caused any air to leak.

The space official has said previously that much of the International Space Station’s equipment is starting to age and has warned there could be an “avalanche” of broken equipment after 2025.