However, Lu said police informed him some of the detained may also face the more serious charges of “organizing others to cross the border illegally”, which carries sentences up to life in jail.
Ren said other lawyers he knew were representing the arrestees were also being denied access.
The prospect of Hong Kongers getting entangled in authoritarian China’s judicial system was the spark that lit seven months of huge and often violent pro-democracy protests last year.
The movement began in response to plan to allow extraditions to the mainland and soon morphed into calls for democracy and greater police accountability.
Since then authorities have cracked down on the city’s democracy movement, prosecuting thousands of protesters as well as leading activists.
In June, Beijing blanketed semi-autonomous Hong Kong in a new security law which toppled the legal firewall between the two.
Under the law, China has claimed jurisdiction for serious national security crimes and empowered its security agents to operate openly in Hong Kong for the first time.