Four people have been arrested in the investigation into the murder of journalist Lyra McKee.
he men, aged 20, 27, 29 and 52, were detained under the Terrorism Act in Derry on Tuesday morning, a PSNI spokesman said.
They are being questioned by detectives at Musgrave Serious Crime Suite in Belfast.
Ms McKee was shot dead while observing disorder in the Creggan area of Derry on April 19, 2019.
The New IRA claimed responsibility for the murder which sparked headlines and revulsion across Ireland and the UK.
PSNI Chief Constable Simon Byrne welcomed the arrests.
He said in a tweet that detectives are "working hard in the pursuit of justice".
Senior investigating officer, Detective Superintendent Jason Murphy, renewed an appeal for information.
"I have always believed that some people within the community know what happened and who was involved," he said.
"I understand that people may be frightened to talk to us.
"I have previously given my personal assurance relating to anonymity for the purpose of this investigation and I renew this assurance today, as we approach the anniversary of Lyra's murder.
"I want the community in Creggan to think about how that horrific attack impacted them personally and how it impacted the entire community.
"We saw wide-scale revulsion after Lyra was murdered and I remain determined to work with the community and local policing to convert that revulsion into tangible evidence to bring those who murdered Lyra to justice.
"I also know that many people were recording mobile phone video clips that night and whilst we had a huge response to my initial appeal for those videos, I believe that others may exist."
Police have asked for anyone with mobile phone footage to upload it to the Major Incident Public Portal at www.MIPP.police.uk.