The North Korean government has yet to publicly acknowledge the U.S. serviceman believed to have crossed the border into the communist country.
Army Private 2nd Class Travis King was seen sprinting across the Military Demarcation Line separating South Korea from North Korea on Tuesday while viewing the Demilitarized Zone (DMZ) alongside a group of tourists.
"Yesterday, the Pentagon reached out to counterparts in the Korean People's Army. My understanding is that those communications have not yet been answered," State Department spokesman Matthew Miller announced Wednesday.
The spokesperson called communications between the U.S. and North Korea "sensitive," and said he could not go into more detail at the time.
"We here at the state department and the U.N. (United Nations) are all continuing to work together on this matter to ascertain information about the wellbeing and whereabouts of Private King," Miller added. "We are still gathering facts, and I want to be very clear that the administration has and will continue to actively work to ensure his safety and return him home to his family."
Neither the ruling Kim Jong Un regime nor the country's legislative assembly have addressed the situation publicly through state media organizations or government offices.
NORTH KOREA DETAINS US SOLDIER WHO CROSSED BORDER 'WITHOUT AUTHORIZATION,' OFFICIALS SAY
King had just finished about two months in a South Korean detention facility following a physical altercation with locals.
After King was arrested and throughout the time he was held at the facility, he made comments that he did not want to come back to America, according to the official.
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King was supposed to board a flight to go back to the U.S. and was escorted to the airport, but the military escort could not follow him past airport security, so King entered the terminal by himself.
King later was alone Tuesday when he left the airport terminal for the tour of the DMZ in a personal capacity in civilian clothes.
Fox News Digital's Chris Pandolfo, Greg Norman, Jennifer Griffin and Liz Friden contributed to this report.