Gulf airline Etihad Airways say all flights into its hub of Abu Dhabi were diverted on Thursday morning due to a technical failure at the airport.

The state-backed carrier said late on Thursday morning that some flights were again being allowed to land but that “significant delays” were expected to continue.

Etihad did not say specifically what caused the diversions, though it happened as dense fog descended over much of the United Arab Emirates.

Etihad and its larger competitors Qatar Airways and Dubai-based Emirates are growing rapidly, and use their Gulf bases as major long-haul aviation transit hubs.

Abu Dhabi International Airport is undergoing a major expansion that includes the construction of a new terminal complex.