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Crown Prince Maha Vajiralongkorn returned to Thailand Wednesday amid growing concerns about the health of his father, King Bhumibol Adulyadej.

The Crown Prince was seen making his way to the Siriraj Hospital, where King Bhumibol is being cared for by doctors. It's not yet known if the Crown Prince has visited the King, who remains in unstable condition, according to a Thai palace statement released Wednesday.

As the Thai nation holds an anxious vigil for their beloved King, hundreds gathered in temples and outside Siriraj Hospital. They held framed portraits of King Bhumibol and prayed for his speedy recovery. Well-wishers were dressed predominantly in pink -- an auspicious color believed to restore health -- and yellow, which is the color of the King.