The discovery of firecrackers in a United Airlines aircraft toilet at Chek Lap Kok has raised a range of concerns from security experts, including fears over a potential hijack risk.
However, authorities played down the discovery and speculated that a passenger left the firecrackers on the plane to avoid bringing them into Hong Kong.
The 6cm-long brown firecrackers were found in an unlocked cupboard under the sink during a routine check on Tuesday night of flight UA895, which had flown from Chicago via San Francisco and was due to continue to Singapore, authorities said.
Deputy Secretary for Security Jennie Chok Pang Yuen-yee urged calm yesterday, saying the 'minor incident' showed security at Chek Lap Kok was effective.
Ms Chok said the explosives in the firecrackers - which appeared to be in their original manufactured form - were not strong enough to cause serious damage to the plane.
Police refused to say what explosives the firecrackers contained because investigations were continuing, but did say they were of a type used for fishing.
The Civil Aviation Department took a low-key approach, failing to notify the public, the media or the US Federal Aviation Administration of the incident until the news leaked yesterday.