Police in Northern Ireland are legally obliged to investigate Bloody Sunday, according to a senior detective.
PSNI Detective Superintendent Ian Harrison said the investigation into the 1972 killings began after the publication of the Saville Inquiry report, "which as a police service, we have a legal obligation to do".
His comments follow the call by the former head of the British army to put a stop to the "macabre charade" that could see Northern Ireland veterans facing legal action.
Lord Bramall said it was "absurd and grossly unfair" that soldiers who took part in the events of Bloody Sunday in Derry in 1972, during which 14 innocent people died, should be questioned by police now.
He accused the PSNI of "harrying" veterans in a "desperate attempt to bring criminal charges" in a piece in The Daily Telegraph.
DS Harrison, from the Legacy Investigation Branch, said the complex investigation into the events of Bloody Sunday was "being carried out by a team of highly professional and competent detectives who will, without fear or favour, follow all investigative opportunities.
"As with any police investigation, this work is being conducted in accordance with statutory responsibilities and the PSNI code of ethics."
Prosecutors have been examining files of evidence against ex-British soldiers who were on the streets of Derry in 1972 when the Parachute Regiment shot and killed 14 civil rights demonstrators.
The new head of the armed forces has spoken out about Northern Ireland veterans being "chased by people making vexatious claims" of wrongdoing, vowing: "That will not happen on my watch."
Chief of the Defence Staff General Nick Carter praised the "remarkable job" done by the British army in Northern Ireland and said groundless allegations against soldiers risked undermining the army's fighting spirit.
He has promised that soldiers facing any investigation would be looked after "to the best of our ability".
MPs have called on the British government to introduce a statute of limitations to end what some claim is a "witch-hunt" against members of the armed forces in Northern Ireland, although official statistics appear to undermine the claim.
A consultation document issued by Northern Ireland Secretary Karen Bradley on dealing with the legacy of the Troubles does not include provision for a statute of limitations, to the anger of many Conservative MPs.
But UK Defence Secretary Gavin Williamson has pledged to look at "all options" to protect veterans from legacy investigations.