HONG KONG (AP) — Hong Kong police raided the private offices of media tycoon and pro-democracy activist Jimmy Lai on Thursday, according to Lai’s aide.

Lai’s aide Mark Simon wrote in a post on Twitter that 14 police officers visited Lai's office and confiscated documents.

Lai, 71, is an outspoken pro-democracy figure who regularly criticizes China’s authoritarian rule and Hong Kong’s government. He is also the founder of media company Next Digital, which operates pro-democracy newspaper Apple Daily.

“I spoke with police they said they would remain until our lawyer arrived,” Simon wrote. “They did not, they took documents and departed before our lawyer arrived.”

In a statement, police confirmed that they had conducted a search operation inside an office in Hong Kong's Kwun Tong district on Thursday, and that “some relevant exhibits were seized for investigation and no person was arrested today.”

The police said that the search operation was related to ten arrests made in August under the national security law, on suspicion of colluding with a foreign country to endanger national security and conspiracy to defraud.

Lai was among those arrested in August, and headquarters of Next Digital were also raided the same day. He was later released on bail.

The raid came hours ahead of Lai’s court appearance Thursday to face charges of joining an unauthorized assembly on June 4. Lai and several other pro-democracy activists, include Lee Cheuk-yan and Joshua Wong, were charged after they participated in a now-banned candlelight vigil marking China’s bloody Tiananmen crackdown in 1989. The vigil is held annually.

Simon said on Twitter that the police were “still trying to make civil disputes into criminal cases.” He said funds that Lai used to support Apple Daily were frozen.

The national security law, which outlaws subversion, secession, terrorism and collusion with foreign forces to intervene in Hong Kong’s internal affairs, has added to fears it will be used to silence dissent.

Pro-democracy supporters say the legislation effectively ends the “one country, two systems” framework under which semi-autonomous Hong Kong has been operating under since Beijing took over the former British colony in 1997.