A white van used as an apparent getaway vehicle flees the scene of a robbery in Fukuoka. Police search for clues in a parking lot where the robbery occurred on April 20. (Videos provided by Kyushu Asahi Broadcasting Co. and the Nishinippon Shimbun and taken by The Asahi Shimbun)

FUKUOKA--Police investigating an afternoon heist of 384 million yen (about $3.5 million) arrested four men on April 21 who were trying to leave Japan with more than 700 million yen in cash.

It is not clear if the suspects are connected to the robbery that was carried out the previous day in the Tenjin district, the biggest shopping and entertainment area in Fukuoka.

The four men, including South Koreans, have denied any involvement in that attack, in which the victim was incapacitated with tear gas. They also do not fit the descriptions of the perpetrators of the robbery, police said.

They were arrested on suspicion of violating the Customs Law, which prohibits travelers from taking more than 1 million yen in cash out of Japan without declaring the money to Japanese authorities.

Two pairs of the four-man group were each carrying more than 300 million yen when they were detained at Fukuoka Airport’s terminal for international flights. They said they had received the money from other people, according to police.

The robbers struck at 12:25 p.m. on April 20 by spraying tear gas into the face of a 29-year-old company employee from Tokyo’s Adachi Ward at a parking lot in the Tenjin district. Two men then grabbed the victim’s suitcase containing 384 million yen and fled the scene in a white van apparently driven by another person.

The victim told police he withdrew the money from Mizuho Bank’s Fukuoka branch nearby and planned to give it to a business partner.

He also said he had informed the bank in advance that he would withdraw a large sum of money.

Police suspect the perpetrators learned about the withdrawal plan and committed a premeditated robbery.

The victim suffered injuries to his face and throat that will require five days to heal.

Fukuoka prefectural police on April 20 set up a headquarters at its Chuo Police Station to investigate the robbery.