(Bloomberg) — Satellite imagery of a parked train suggests Kim Jong Un may have been at his holiday compound in North Korea’s east coast this week as speculation swirls about the leader’s health, according to the monitoring group 38 North.

China sent a team that included health-care experts to the neighboring country to advise on Kim, Reuters reported, citing three people familiar with the matter. Kim has been out of the public eye for a few weeks, and was reported to be in critical condition after undergoing cardiovascular surgery.

U.S. officials said Monday they were told of Kim’s condition after the surgery, though they were unsure of his current health. President Donald Trump on Thursday cast doubt about a CNN report saying the North Korean leader was very ill. Officials with the National Security Council at the White House declined to comment on Saturday.

Kim was conspicuously absent from birthday celebrations on April 15 of his grandfather and state founder Kim Il Sung. He has not been seen since a politburo meeting on April 11, raising speculation about his condition. The state-run Korean Central News Agency reported that Kim sent a message Wednesday to Syrian President Bashar al-Assad. Letters of this sort are reported frequently.

Read more: ‘Materialism Will One Day Bring Change.’ Why a Senior Defector Believes North Korea’s Days Are Numbered

A delegation led by a senior member of the Chinese Communist Party’s International Liaison Department — which deals with North Korea relations — departed Beijing on Thursday, Reuters said, adding it wasn’t able to immediately determine what the trip signaled about Kim’s health. The health of the North Korean leader is one of the most closely guarded secrets in the isolated state, known only to a few people in its inner circle.

The head of the Korean Friendship Association, a group that says it receives official information from North Korea, on Saturday disputed news reports that Kim, 36, is gravely ill. “Information about the serious state of health of our Marshal Kim Jong Un is false and malicious,” Alejandro Cao de ­Benos said in a tweet.

Cao, who was featured in the 2015 documentary The Propaganda Game, didn’t say where he got the information and declined further comment when contacted by Bloomberg.

Analysts at 38 North, a website devoted to analysis of North Korea, said a train probably belong to Kim has been parked at the railway station that serves the private compound in Wonsan since at least April 21. Wonsan is about 230 kilometers (143 miles) from Pyongyang.

“Imagery indicates the train arrived sometime before April 21 and was still present on April 23, when it appeared to be repositioned for departure,” the analysts said. “There was no indication when that departure might take place.”

The train’s presence doesn’t prove Kim’s whereabouts or indicate anything about his health, they added.

— With assistance from Jihye Lee.

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