Hong Kong denied entry to an exiled leader of the Tiananmen Square pro-democracy protests, exiled in the US, who wanted to visit his ailing mother in mainland China, according to pan-democratic lawmakers. Xiong Yan, who was jailed for his role in the 1989 protests, was interrogated by immigration officers at Chek Lap Kok airport for several hours on Thursday night after his arrival. He was put on a return flight to Las Vegas by midnight, said Democratic Party lawmaker Albert Ho Chun-yan, who also leads the Hong Kong Alliance in Support of Patriotic Democratic Movements of China. The incident showed the government was lengthening a rumoured "blacklist" of dissidents, as Xiong had entered the city successfully six years ago, said Lee Cheuk-yan, secretary of the alliance, which stages the annual June 4 candlelight vigil for Tiananmen victims. "Xiong attended the vigil and even spoke on stage when he was let into the city in 2009," Lee said. "Apparently he was added to the government's blacklist afterwards. The case proves the so-called blacklist not only really exists but is also expanding." The Labour Party stalwart added: "He was holding a US passport with his name written as 'Yan Xiong' instead of the other way round, so maybe that was why the Hong Kong government missed it last time." Lee had planned to meet Xiong when he arrived at Chek Lap Kok airport. After being barred from entry, Xiong expressed his love for his mother in a poem he wrote before returning to the United States. "I have arrived in Hong Kong. Picturing your weak face … though we cannot get together on earth, we will definitely meet each other again in heaven," read the poem, obtained by League of Social Democrats chairman Leung Kwok-hung. In 1989, Xiong, a leading member of the Students' Dialogue Group, was jailed for two years after the crackdown and fled to the US in 1992. The Immigration Department would not to comment on individual cases, saying its decisions on whether to grant entry were based on Hong Kong law and prevailing immigration policies. Hong Kong turned away another US-based June 4 activist, Dr Yang Jianli, for the fourth time, in April last year.