North Korean leader Kim Jong-un has recently visited China, his first known overseas trip since taking power in 2011, Bloomberg reported on Monday, citing unidentified people. More details of the trip, such as how long Kim would stay in China or who he would meet, are unavailable.

Bloomberg said their sources of information asked not to be identified because of the sensitivity of the matter. North and South Korea are scheduled to hold talks at the end of April. United States President Donald Trump has also accepted an invitation from Kim to meet him.

Speculation about Kim’s China visit arose when Japan’s Kyodo News reported on Monday that a special train, which may have carried a high-ranking North Korean official, passed through the Chinese border city of Dandong. A car bearing the licence plate of the North Korean embassy was spotted at the Great Hall of the People, a Chinese government building used for official purposes, on Monday.

Moreover, severe traffic regulations have been imposed in Beijing, and restaurants around the Sino-Korean Friendship Bridge linking Dandong with the Sinuiju town in North Korea have suspended reservations for rooms facing the North Korean side, Kyodo News said.

Officials at the White House were not forthcoming about Kim’s China visit, Bloomberg reported. White House Deputy Press Secretary Raj Shah told reporters on Monday that he could not confirm reports of the trip. “We don’t know if it is really true,” he said. “What I’ll just state, though, is that where we are with North Korea is in a better place than we used to be because the president’s maximum pressure campaign.”