Hong Kong customs officials announced on Tuesday that nine Singaporean armed vehicles seized two months ago will be returned after the completion of an investigation.

The Singaporean vehicles were impounded by customs on Nov 23"because there was a suspected breach of Hong Kong law", said Roy Tang, commissioner of customs and excise of the Hong Kong Special Administrative Region.

The armed vehicles were inside a cargo ship from Taiwan that was passing through Hong Kong. They were on their way back to Singapore following a military drill in Taiwan.

Tang said that customs has finished its investigation. The case may lead to criminal prosecution, according to a news release from the Hong Kong government.

"Import, export and transshipment/transit of strategic commodities in breach of licensing requirements are criminal offenses punishable under the Hong Kong law," he said, adding that the military vehicles and the associated equipment will be returned to Singapore.

In a statement released on Tuesday, Singapore's Ministry of Foreign Affairs said that Prime Minister Lee Hsien Loong had thanked Hong Kong Chief Executive Leung Chun-ying for resolving the matter.

"This is a positive outcome," the Singaporean ministry said.

On Jan 17 in Beijing, Foreign Ministry spokeswoman Hua Chunying urged the Singaporean government to stick to the one-China principle when she was asked about the seizure of the vehicles.

China attaches great importance to its relationship with Singapore, and at the same time, China's stance on the one-China principle is firm and unchanged, she said.

Jia Duqiang, a senior researcher in Southeast Asia studies at the Chinese Academy of Social Sciences, said that by seizing the vehicles, China sent a signal to Singapore that the city-state should stick to the one-China principle, especially as Taiwan authorities led by Tsai Ing-wen are challenging Beijing on sovereignty.

Returning the vehicles is a positive sign for the China-Singapore relationship, he said, adding that bilateral ties have been frustrated in recent months as a result of what he called Singapore's "improper remarks" on China's stance on the South China Sea issue.

In July, Singapore asked "all parties to fully respect" the ruling of an arbitration case on South China Sea territorial disputes. China insisted that the ruling is "null and void", and has no binding force.