Hong Kong’s security chief has warned that booksellers are responsible for ensuring that the titles they sell do not violate national security legislation. His comments came a day after police raided two independent bookstores and arrested five people on suspicion of sedition.

Secretary for Security Chris Tang Ping-keung reiterated on Thursday that the government would not draw up a list of banned books, arguing that offenders could circumvent such a measure simply by changing a book’s title.

According to police, the arrests followed a report from the Customs and Excise Department, which had intercepted a shipment of books from overseas that were considered seditious.

“If you are a bookseller, you have a responsibility to ensure that the books you sell do not endanger national security,” Tang said. “It is like a food retailer, who must ensure that the food being sold does not make people ill or contain poisonous substances.”

Tang said the law clearly defines seditious acts and that the authorities would make arrests and bring charges whenever sufficient evidence was available.

“We target the content, not the book title itself,” he said. “If we relied solely on a list of titles, many people would simply change the titles of books that are illegal or endanger national security and claim they are not on the blacklist and therefore cannot be arrested.”

Tang also dismissed concerns that the authorities were targeting bookstores, saying police would enforce the law whenever seditious materials were found, regardless of the location.

A source previously said the books under suspicion included works by the late opposition lawmaker Shiu Ka-chun and “Stay,” the memoir published last year by former Democratic Party chairwoman Emily Lau Wai-hing.