However, officials said they would shut the airport down if the damage constituted a threat to aircraft and passengers.

"There are cracks at 25 locations and the areas have been closed for reconstruction," AOT senior executive vice president Somchai Sawasdeepon said.

"This problem has affected our capacity slightly. Now, we can accommodate 60 flights an hour down from 72."

But Defence Ministry deputy permanent secretary Admiral Bannavit Kengrien threatened to shut down Suvarnabhumi if an investigation proved cracks could lead to damage. A team of Army engineers was assessing them.

"If the investigation finds runways are dangerous we will immediately recommend the closing of Suvarnabhumi to prevent harm to passengers," Bannavit said.

The investigation would be completed by the end of the month.

Bannavit lashed out at the previous government, blaming it for the current construction concerns.

He claimed the Thaksin-Shinawatra administration had abandoned a "defective child" for others to raise.

He said wherever one looked there was the legacy of alleged corruption by the Thaksin government - baggage scanners, telephone lines, baggage trolleys and a hotel fiasco.

He claimed the airport difficulties were an "indignity" and that the airport hotel had cost the government Bt500 million over five years.

"Thaksin declared there was no corruption at the airport but we have found corruption in every tiny detail. Something we were once proud of has turned into a graveyard," Bannavit said.

Meanwhile, Transport Minister Theera Haocharoen said AOT would quickly investigate the cracks that may have been caused by sub-standard repairs at an earlier time.

He was considering punishment for those involved.

AOT executive Somchai said the cracks were "unexpected" and had been caused by flooding during the wet season.

A construction joint venture is responsible for repairs. The IOT group is made up of Italian-Thai Development plus the Obayashi and Takenak corporations.

The runways are insured and the policy held by Diphaya Insurance.

Repair costs had yet to be calculated but would be in the vicinity of Bt1 billion, Somchai said, adding a claim would have to be made soon because the policy expires in August.

The AOT board meets on Thursday to discuss the cracks crisis.