(CNN) -- The family of a Korean-American missionary believed held in North Korea said Tuesday they are working with U.S. officials to get him returned home.
Robert Park told relatives before Christmas that he was trying to sneak into the isolated communist state to bring a message of "Christ's love and forgiveness" to North Korean leader Kim Jong Il. In a written statement issued Tuesday on the family's behalf, his brother, Paul Park, said Park's well-being "has been a source of ongoing concern and anxiety" since they received reports he had entered North Korea.
"He is a very special member of our family. We miss having his love and compassion in our home," the family statement said. "I don't know where he's being held, but if he can receive this message, we want him to know we love him, we miss him and we are waiting anxiously for the opportunity to be reunited with him."
Paul Park said his San Diego, California-area family is working with the U.S. State Department and members of Congress to bring about his "eventual safe return."
North Korea announced Tuesday that it was holding an American who entered the country illegally from China on Christmas Eve. The state-run Korea Central News Agency did not identify the man, who it said was "now under investigation by a relevant organ."
Monday, State Department spokesman Ian Kelly said Washington was concerned by reports that Park had gone into North Korea but could not confirm them. Washington and Pyongyang have no diplomatic relations, but Kelly said the Swedish Embassy -- which looks after U.S. interests in North Korea -- has offered to try to find out more.
A South Korean Web site last week posted a copy of the letter it said Park was trying to deliver to Kim, which urged the North Korean leader in the name of Jesus Christ to free political prisoners and "open your borders so that we may bring food, provisions, medicine, necessities, and assistance to those who are struggling to survive."
North Korean authorities take a dim view of people who enter the country without authorization. Two American journalists who were arrested along the North Korean-Chinese border in March faced a 12-year sentence at hard labor, but were released after a meeting between Kim and former U.S. President Bill Clinton in Pyongyang.
But Park's parents told CNN affiliate KFMB that their son was willing to risk his life to deliver his message to Kim.