U.S. President Donald Trump has hinted at the imminent release of Americans detained in North Korea, just weeks ahead of a planned summit between him and the North’s leader, Kim Jong Un.

“As everybody is aware, the past Administration has long been asking for three hostages to be released from a North Korean Labor camp, but to no avail. Stay tuned!” Trump wrote Wednesday on Twitter.

The U.S. government said it is looking into reports that the three Americans had been relocated from a labor camp to a hotel near Pyongyang ahead of the Kim-Trump summit.

Securing their freedom would be a key win for Trump, and administration officials have pressed for their release as a show of goodwill by North Korea ahead of the meeting, expected for later this month or early June.

On Wednesday, South Korea’s Yonhap news agency quoted a South Korean activist as saying the North had relocated the three Americans from a labor camp to a hotel on the outskirts of Pyongyang.

Yonhap said Choi Sung-yong, who heads a group for families of South Koreans abducted by the North, cited a resident in Pyongyang as saying Kim Hak-song, Kim Dong-chul and Tony Kim, who is also known as Kim Sang-duk, were moved in early April following instructions from authorities.

“We cannot confirm the validity of these reports,” a U.S. State Department spokesperson told The Japan Times.

“The welfare and safety of U.S. citizens abroad is one of the highest priorities of the Department of State. We are working to see U.S. citizens who are detained in North Korea come home as soon as possible,” the spokesperson added.

Tony Kim’s son, Sol Kim, said in a statement that he had received no indication that the three detainees would be released soon.

“My family and I appreciate the ongoing support for the release of the 3 Americans (#USA3) detained in North Korea including my dad, Tony Kim,” he said. “We are hopeful but we have no indication that they have been released. Thank you for your continued prayers and efforts to help bring them home. We look forward to all of the families being reunited very soon.”

Among the three detainees, Kim Dong-chul, a South Korean-born American pastor, was arrested by North Korea in 2015 on charges of spying and sentenced in 2016 to 10 years of hard labor. Kim Hak-song and Tony Kim, both working for Pyongyang University of Science and Technology, were detained last year on suspicion of “hostile acts.”

Their release was discussed when then-CIA Director Mike Pompeo, who is now secretary of state, traveled to Pyongyang last month, according to The Wall Street Journal.

Trump administration officials, including national security adviser John Bolton, have said that releasing the hostages would be “an opportunity” for the North to “demonstrate their authenticity” ahead of the summit.

CNN reported Thursday that their release was also discussed at talks in Stockholm between North Korean Foreign Minister Ri Yong Ho and Swedish counterpart Margot Wallstrom in March. Sweden represents Washington’s interests in the North.

Citing an unidentified official with knowledge of the negotiations, the report said Ri had proposed their release, but U.S. officials insisted at the time that it “not be related or used to loosen the main issue of denuclearization.”

Marking North Korea Freedom Week, which runs through Saturday, the State Department issued a statement Wednesday saying it remains “gravely concerned and deeply troubled” by human rights issues in “one of the most repressive and abusive governments in the world.”

“In tandem with the maximum pressure campaign, we will continue to press for accountability for those responsible,” State Department spokeswoman Heather Nauert said in a statement. “We are also going to continue our efforts to increase the flow of independent information into, out of, and within this isolated state to present everyday North Koreans with a more realistic picture of the outside world.”