A convicted sex offender under investigation for another alleged sex crime fled abroad while wearing an electronic monitoring device, and was repatriated, police said on Tuesday.

The Seoul Nowon Police Station said it arrested the man surnamed Shin at the Incheon International Airport last Thursday after he was sent back from Ho Chi Minh City with the cooperation of Vietnamese police.

It is the first time a criminal under surveillance left the country while wearing an electronic tag. A man convicted of sex crimes ran off to Japan last month after breaking his ankle monitor, and has not been located yet.

Shin, who has a history of twice damaging his ankle monitor, was under police investigation for allegedly raping a woman after drugging her last month.

The police had requested a warrant to detain Shin, but the court denied it, saying he was unlikely to flee as he was wearing an ankle monitor.

The police said it did not apply for an overseas travel ban on Shin because the court had said he was a low flight risk.

Shin boarded a plane bound for Ho Chi Minh City last Wednesday, and his probation office alerted the police after they lost signal from his device.

The probation office had called him earlier asking why he went to the airport, and Shin said that he had work to do at a logistics center there.

When his electronic tag was detected at the airport security checkpoint, security officers identified him and learned that he was an ex-convict of sex crimes.

They did not ask for any documentation, however, when he lied that he had permission from the Justice Ministry to travel abroad.

The airport immigration counter didn’t stop him either.

According to the Justice Ministry, the airport immigration office has no way of finding out whether someone wearing an electronic tag had permission to travel abroad or not, unless the ministry has forbidden that person from exiting the country.

Upon request from the Korean police, the Vietnamese police nabbed Shin at the Ho Chi Minh City airport and sent him back to Korea.

The police detained Shin on charges of violating the laws on electronic tags and probation, in addition to rape and violation of the law on narcotics. The police plan to send Shin’s case to the prosecution for indictment.

Of the nearly 3,000 people currently wearing ankle monitors in Korea, 450 have traveled abroad with permission from the Justice Ministry. Five of them have failed to return.

The ministry said it is looking into measures that would allow the immigration office to confirm whether people wearing electronic tags have received permission to travel abroad through close cooperation with the probation office.

By Kim So-hyun (sophie@heraldcorp.com)