North Korea has detained another U.S. citizen.

The Korean-American man was arrested Friday at Pyongyang International Airport as he was preparing to leave the country, the South Korea’s Yonhap news agency reports.

The Swedish Embassy in Pyongyang said it was aware of a Korean-American citizen being detained recently, but could not comment further. The embassy looks after consular affairs for the United States in North Korea because the two countries do not have diplomatic relations.

The man, identified only by his surname Kim, was reported to have been discussing relief activities in North Korea for about a month. The news agency, citing unnamed sources, said he is in his late 50s and has been involved in aid and relief programs to North Korea and was a former professor at the Yanbian University of Science and Technology in China.

The reason for his arrest was not immediately clear.

His arrest brings the number of Americans detained by North Korea to three.

North Korea has in the past detained U.S. citizens to use as bargaining chips in its negotiations with Washington.

The two other Americans are currently detained in North Korea. Last year, Otto Warmbier, then a 21-year-old University of Virginia student from suburban Cincinnati, was sentenced to 15 years of hard labor in prison after he confessed to trying to steal a propaganda banner. Kim Dong Chul, who was born in South Korea but is also believed to have U.S. citizenship, is serving a sentence of 10 years for espionage.

At least one other foreigner, a Canadian pastor, is also being detained in North Korea. Hyeon Soo Lim, a South Korean-born Canadian citizen in his 60s, was convicted and sentenced to life in prison in 2015 on charges of trying to use religion to destroy the North Korean system and helping U.S. and South Korean authorities lure and abduct North Korean citizens.

The Associated Press contributed to this report.
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