North Korea has so far declined to respond to US outreach about the fate of a US soldier who fled into the isolated country in what may have been an effort to escape court martial after being charged with assault, the State Department said.

“Yesterday, the Pentagon reached out to counterparts from the Korean People’s Army,” State Department spokesman Matthew Miller told reporters Wednesday. “My understanding is that those communications have not yet been answered.”

Miller said the US has engaged with officials from South Korea and with Sweden, which acts as a diplomatic liaison to North Korea, and will continue to “work to ensure his safety and return him out to his family.”

On Tuesday, the Army said Private Second Class Travis King, 23, crossed over the border between South and North Korea. A US official familiar with the matter said King had been released from South Korean detention where he had been held on charges of assaulting two Koreans, and was facing the possibility of being expelled from the military after being returned to the US.

Apart from the assault, the suspected border-crosser kicked and broke the door of a police car in Seoul last October, shouting profanities directed at the police and US army when taken into custody, court records showed. He was fined 5 million won ($4,000) by a district court in the city over the incident, according to the records.

King’s mother, Claudine Gates, told ABC News that she just wants her son to come home and was shocked to hear he had entered North Korea.

“I can’t see Travis doing anything like that,” ABC quoted her as saying. As of midday Wednesday, North Korea hadn’t commented on the incident.

Although South Korean and American soldiers keep a close eye on those who visit the area, the border between the Koreas in the Joint Security Area in the Panmunjom so-called truce village is marked by a concrete slab only a few inches off the ground and is easy to cross.