The man charged over Friday's twin mosque attacks in the New Zealand city of Christchurch is believed to have acted alone, police say.
Australian Brenton Tarrant, 28, a self-described white supremacist, live-streamed the attack on Facebook.
Three others arrested afterwards are not believed to have been involved, Police Commissioner Mike Bush said, but added that he could not be conclusive.
Fifty people were killed and 50 injured in what is New Zealand's worst attack.
Some 34 people remain in hospital receiving treatment for injuries ranging from severe gunshot wounds to "relatively superficial soft tissue injuries", authorities said.
What is the latest?
Speaking to reporters on Sunday, New Zealand Prime Minister Jacinda Ardern said that cabinet meetings would take place on Monday to discuss issues including gun policy reform. "There will be changes to our gun laws," she said. She added that parliament would pay tribute to victims in the house on Tuesday.
Ms Ardern said she expected the bodies of all those killed to be returned to their families by Wednesday.
She also said that "there are further questions to be answered" regarding the role of social media sites such as Facebook, which was used to broadcast live footage of the attacks.
"These social media platforms have a wide reach, and this is a problem that goes way beyond New Zealand," she said.
Meanwhile, Facebook has said that as many as 1.5m videos of the attack were removed from its platform in the first 24 hours. It said it was also removing "all edited versions of the video that do not show graphic content".
Ms Ardern confirmed that her office had received a document from the suspect nine minutes before the attacks began, but that it did not contain any specific details, such as a location. She said it was forwarded to the security services within two minutes.
Members of the public visit a memorial at the Botanical Gardens in Christchurch on Sunday
Separately, Commissioner Bush said that authorities were working as fast as they could to finish formally identifying the victims of the attacks at the Al Noor and Linwood mosques.
He added that it was a sensitive process and that he was "aware of the cultural and religious needs".
Who has been linked to the attacks?
On Saturday, the main suspect appeared in court in a white prison shirt and handcuffs, smiling for the cameras.
He has been charged with one count of murder - with more charges expected to follow.
Commissioner Bush told a news conference that the 28-year-old was the only person charged with carrying out the shootings.
"He was stopped because he was believed to be a direct threat, our staff acted with absolute courage in intervening and had to use some force... they put themselves in harm's way to stop any further attack - and I do believe they did prevent further attacks," he said.
Commissioner Bush said police did not believe that two people arrested near the scene were involved. A woman was released without charge and a man was charged with firearms offences.
An 18-year-old was also arrested but his involvement was said to be "tangential" and he would appear in court on Monday, Commissioner Bush added.
However he cautioned: "I will not be saying anything conclusive until we are absolutely convinced as to how many people were involved."
None of those detained had a criminal record.
Mr Tarrant has been remanded in custody without a plea and is due to appear in court again on 5 April.
The presiding judge ruled that the suspect's face should be pixellated in photographs and moving images to preserve his fair trial rights.
Ms Ardern said Mr Tarrant had a firearms licence and owned five guns.-BBC
