More than 10 days after bookseller Lee Bo went missing, the Hong Kong police have set up a 24-hour hotline for the investigation. Members of the public who have information on the disappearances are urged to contact the Regional Missing Person Unit at 6764 4385. Meanwhile, pressure is mounting on the Hong Kong government to demand answers from mainland authorities on the whereabouts of missing bookseller Lee Bo, with today being the deadline for them to respond under a reciprocal mechanism. But Chief Executive Leung Chun-ying suggested that today was not a definite deadline. “Sometimes it takes longer, and sometimes the otherwise, for mainland authorities to respond on cases like these … this case was reported to the Hong Kong police on January 1, and it has been 11 days since then, but there were cases in the past which took longer for mainland authorities to respond to,” Leung said this morning. READ MORE: Hong Kong justice minister pledges ‘full and thorough’ probe into missing bookseller mystery Lee, who holds a British passport, was the fifth Hong Kong bookseller involved with publications banned in mainland China to go missing in the past two months. The disappearances prompted thousands to take to the streets on Sunday in protest. On Sunday, Legislative Council President Jasper Tsang Yok-sing said the government should consider appealing to Beijing to “urge the relevant departments to cooperate” with Hong Kong. But Leung declined to confirm whether he appealed to the central government. “I have relayed Hong Kong people’s concern to the relevant departments … we are following up and seeking help from different levels and sources,” Leung said. Leung reiterated that he was highly concerned about the case, which has sparked global concern about Beijing’s growing influence in Hong Kong. Under the arrangement, law enforcement agencies on the mainland must notify the city’s police within 14 days if any Hong Kong resident is detained across the border, Democratic Party lawmaker James To Kun-sun was told by the Hong Kong force earlier. Lee disappeared on December 30. Watch: Thousands of protesters march to demand release of missing booksellers In a letter to Chinese president Xi Jinping, Democratic Party chairwoman Emily Lau Wai-hing wrote that Hong Kong people were in the midst of a “confidence crisis” in the “one country, two systems” principle due to the booksellers’ disappearances. “Hong Kong citizens are very worried that the Causeway Bay Books incident was not the first and would not be the last incident of mainland officers carrying out law enforcement actions recklessly across the border,” she wrote. “After the Lee Bo incident, Hong Kong citizens have scrambled to apply for British National (Overseas) passports. This has reflected that they have a confidence crisis over the ‘one country, two systems’ principle. We believe this is a situation the central government is not happy to see.” Lau urged Beijing to investigate the incident and offer a public explanation of what happened. Lawmaker Albert Ho Chun-yan, suggested the relevant mainland authorities were struggling to decide what they should do next. If they told Hong Kong police that Lee was indeed being held across the border, they would have to come up with a reasonable explanation as to how he got there, Ho said on Monday. “And don’t forget that other booksellers have already been missing for longer than 14 days. The mainland has not notified Hong Kong on those cases,” he said, referring to four associates of Lee who have vanished since October. Labour Party lawmaker Lee Cheuk-yan did not believe the mainland would notify Hong Kong by the deadline. He said there was a “grey area” under the mechanism because the bookseller had said he was“assisting with an investigation” across the border and did not say he was being detained. “The police commissioner said the force had contacted the Guangdong Provincial Public Security Department. But I think Chief Executive Leung Chun-ying should personally contact the mainland authorities on this matter,” he said. Watch: Chief Executive CY Leung ‘very concerned’ about missing booksellers Richard Tsoi Yiu-cheong, deputy chairman of the Hong Kong Alliance in Support of Patriotic Democratic Movements of China, said Hong Kong people would only become more suspicious if the mainland authorities did not reply. The alliance organised a protest on Sunday with 6,000 people taking to the streets to demand Beijing respect the “one country, two systems” principle. A police spokesman would only say the force had been in “close contact” with its mainland counterparts. Lee ran Causeway Bay Books, which specialised in books critical of the Communist Party. His disappearance led to speculation that mainland security agents had abducted him from Hong Kong, something that would be unlawful. Lee’s wife, Sophie Choi Ka-ping, stopped writing columns for the pro-Beijing newspaper Ta Kung Pao after a run of 20 years. Her last column appeared in the newspaper last Friday.