Victims of an attempted robbery case that happened at Tokyo¡¯s Haneda Airport on Friday had about ?95 million ($614,000) in foreign currency stolen in a different incident in the past, investigative sources said on Sunday.

Last year, their vehicles were broken into at a parking facility at the airport, located in Tokyo¡¯s Ota Ward, and also at another parking lot in the Chuo Ward in the Japanese capital, according to the sources.

Tokyo¡¯s Metropolitan Police Department is investigating the possibility that the victims had been targeted by people who knew they were often transporting a large amount of cash in suitcases.

Of the four men who fell victim to Friday¡¯s attempted robbery case, a company president in his 30s has told police that he buys gold almost every day, gets cash by selling it and exchanges the money in Hong Kong.

In the latest incident, a group of four individuals in a white car approached a vehicle of the four men on the third floor of a multilevel parking facility adjacent to Haneda Airport¡¯s Terminal 3 at around 12:10 a.m. on Friday. The group attacked the victims¡¯ vehicle with a hammer and spray, but the attackers fled without stealing anything.

The victims were on their way to Hong Kong with about ?190 million in cash in suitcases.

In Hong Kong on Friday morning, two men were robbed of more than ?50 million in cash. The two were among the four victims of the attempted robbery case at Haneda.

Over the Hong Kong case, six people, including three Japanese citizens, were arrested by local police on Saturday.

In police questioning, one of the three Japanese suspects claimed themselves to be a victim, having transported the cash from Japan to Hong Kong with a man in his 50s, but the person is believed to have provided information related to the crime to the robbery group and cooperated in the offense.

The other three arrestees are two from mainland China and one from Hong Kong.

According to Hong Kong media, the man in his 50s and the other individual arrived in Hong Kong by air Friday morning and then took a taxi to a foreign exchange office in Sheung Wan, part of the region. Soon after getting off the taxi, the man was assaulted and robbed of a backpack containing cash.

Last December, two Chinese employees of a Japanese company were robbed of about ?1 billion in cash in Sheung Wan, which has many currency exchange offices.