SEOUL--A South Korean official who disappeared off a government ship near the disputed sea boundary with North Korea this week may be in North Korea, South Korea’s Defense Ministry said Wednesday.

The ministry said the 47-year-old official was aboard a government vessel that was checking on potential illegal fishing near a South Korean border island. Colleagues noticed the man was missing at lunch time and found only his shoes still on the vessel, prompting a so-far fruitless search involving aircraft and ships.

In its statement, the Defense Ministry said it had information that the missing official was on North Korean shores on Tuesday afternoon. The ministry did not elaborate on how it obtained that information.

The ministry said officials will contact North Korea to ask about the missing official and take other steps to find more details.

The Ministry of Oceans and Fisheries, which was operating the vessel the man was on Monday, said 18 people were on board when the man went missing. It didn’t provide information about the missing official.

More than 30,000 North Koreans have fled to South Korea in the past 20 years for political and economic reasons, but it’s highly unusual for a South Korean national to defect to North Korea.

At the height of Cold War rivalry, North Korea often forcibly towed South Korean fishing boats operating near the sea boundary into its waters, holding some of those on board and returning others. No such incidents have been reported in recent times.

The poorly marked sea boundary is where several inter-Korean naval skirmishes and deadly attacks blamed on North Korea have occurred in recent years.

Ties between the two Koreas remain strained amid a deadlock in nuclear talks between North Korea and the United States.