Apple Daily says the police have given the newspaper until Monday to make a claim of legal professional privilege on certain documents seized during a raid at its offices this week.

Its editor-in-chief, Ryan Law, said on Wednesday that the company's legal department had received a letter saying the papers will not be unsealed until next week.

He said the documents in question concerned files relating to Next Media’s CEO, Cheung Kim-hung, executive director Chow Tat-kuen, and the Apple Daily Charitable Foundation.

The newspaper has said it plans to apply for a temporary injunction to prevent officers from going through certain journalistic material it says was seized during the raid in Tseung Kwan O on Monday, but it's not clear whether the same deadline applies.

About 200 police officers raided the company's headquarters on Monday as part of a national security probe which saw the arrest of the newspaper's founder, Jimmy Lai and his two sons. Several executives were also arrested on suspicion of conspiracy to defraud.

Lai and the others arrested were released on police bail on Tuesday.

Police said they took a cautious approach to the raid on Monday and did not take journalistic material, nor get in the way of the newspaper's production.

Senior superintendent Li Kwai-wah of the police's new national security branch said some officers were seen “scanning through” documents on reporters’ desks because they were simply trying to look for evidence.