Some supporters held yellow umbrellas -- a symbol of the Occupy protest movement -- while others chanted slogans such as, "I want true universal suffrage" and "We will fight to the end."
Inside, Occupy Central co-founders Chan Kin-man, Benny Tai Yiu-ting and the Reverend Chu Yiu-ming were being probed -- along with lawmaker Gary Fan Kwok-wai -- about their role in protests that saw thousands of demonstrators leave the city in political deadlock.
The trio is the last group of pro-democracy activists to be rounded up over the last two weeks, the South China Morning Post reported Saturday. Since early January, lawmakers, students and members of political have been arrested for similar questioning.
The Post added that a team of more than 10 lawyers had accompanied the Occupy co-founders to the station.
A police spokesman said that the men had been arrested earlier Saturday on suspicion of organizing, participating and convening an unauthorized assembly and inciting others to take part in it.
As part of the questioning, they were shown videos of their involvement in the unlawful assembly -- one shot by Occupy leaders months ahead of the protests to promote the movement.
The Post reported that the trio remained silent throughout, but reported Tai as later saying that he had "faith in Hong Kong’s rule of law system."
He added that they would argue their case in court.
Last year's protests had called for a fully democratic chief executive election with open nominations in 2017.
Beginning in late September, they were a response to the Chinese government’s decision to impose a condition that the candidates first be approved by a body loyal to Beijing.