Five editors and executives at pro-democracy Apple Daily newspaper were arrested Thursday under Hong Kong’s national security law, its stock was halted and police were searching its offices in moves raising concerns about the media’s future in the city.

Apple Daily is known for its strong pro-democracy stance and often criticizes and condemns the Chinese and Hong Kong governments for tightening control over the city.

Hong Kong authorities have been intensifying a crackdown on dissent following months of mass anti-government protests in 2019.

Apple Daily’s chief editor Ryan Law, Next Digital CEO Cheung Kim-hung, the publisher’s chief operating officer and two other editors were arrested, according to Apple Daily, the South China Morning Post and other local media.

The government said security police had arrested five directors of a company for “suspected contravention” of the national security law.