Hong Kong's Independent Commission Against Corruption said the arrests were in connection with the use of sub-standard materials to build a railway link to the airport.

"During the past several months, the ICAC has been carrying out an investigation following corruption allegations relating to the substandard foundation works at the Northern Site of the Hong Kong Station," the ICAC said in a statement.

The ICAC said it seized 14 handguns and about 1,000 rounds of ammunition during the anti-corruption operation which started on Monday.

Those arrested include two shareholders and five employees of subcontractors, as well as technicians involved in the airport railway project. Four people have now been released on bail, and no-one has yet been charged.

The Commission said bribes may have been offered to cover up the use of the poor materials, and there are allegations that site engineering staff falsified reports on the depth of holes bored at the site.

Construction bribes

Public Tranport officials insist the new service to the airport is safe and a statement from the Corporation which runs the railway, said the investigation didn't involve airport railway stations now being used by the public.

Hong Kong's new airport has not got off to a flying start

But a BBC correspondent says the scandal has raised concerns about whether the construction work has been properly supervised and if it fulfils government safety standards.

The airport has been hit by operational problems since it opened last week.

In an attempt to relieve cargo congestion, the authorities on the mainland have now said Hong Kong airlines can use the airport in Shenzhen for the movement of goods.

Security lapses under fire

Hong Kong's legislature is to investigate alleged lapses in security at the territory's new airport.

Problems for passengers are being smoothed out

James To, chairman of the Legco Security Panel, was quoted as saying members were worried about security breaches that might have violated international air safety rules.

He said the issue would be taken up as a matter of priority.