Seoul, South Korea CNN  — 

An unidentified man who crossed the heavily armed border from South Korea into North Korea on Sunday is presumed to be a North Korean defector who made the journey in the opposite direction more than a year ago, according to the South Korean Defense Ministry.

In a statement Monday, the Defense Ministry said based on CCTV footage they presumed the man who made the rare crossing to the North on Sunday had first entered the South in November 2020. Relevant authorities were still verifying the facts, the ministry added.

The man was spotted at the eastern front of the Demilitarized Zone (DMZ) at around 9:20 p.m. local time on Saturday, South Korea’s Joint Chiefs of Staff (JCS) said. The man was detected by the military with the use of a thermal observation device.

The JCS said troops were dispatched but they were unable to find the man, who crossed the Military Demarcation Line into North Korea at around 10:40 p.m.

A military official said security cameras had earlier captured the man climbing a barbed wire fence at around 6:40 p.m. Saturday, but the guard on CCTV duty had missed it. The official said it is unknown whether the man was still alive.

“We sent a notice to North Korea to protect our people yesterday and there has been no response from North Korea,” South Korea’s Defense Ministry spokesman Boo Seung-chan said Monday.

There were “no unusual movements of the North Korean military” in relation to Sunday’s incident, he added.

North Korean state media did not report on any crossings over the DMZ overnight.