A murder investigation into the Bloody Sunday atrocity in Derry could take up to four years, according to the police in charge of the new enquiry.

As the British governmentconfirmed that police in Northern Ireland will investigate the shooting of 14 people to their deaths in Derry almost 40 years ago, the officer in charge of the case warned of its enormity.

A statement from the Police Service of Northern Ireland quoted chief constable Matt Baggott on the complexity of the investigation.

British soldiers shot 13 civil rights marchers dead on the day in Derry almost 40 years ago, with another victim dying in hospital weeks later.

The PSNI statement confirmed that up to 30 officers will be involved in the case, which could take up to four years to investigate.

The decision to treat the Bloody Sunday massacre as a murder case comes after Northern Ireland’s Public Prosecution Service and the PSNI reviewed the findings of the Saville inquiry, which found that all those shot or injured were innocent.

The Irish Times reports that Lord Saville’s 5,000-page report was deeply critical of the British paratroopers deployed in Derry on the day and of the orders given by their commanding officer.

The report was finally published in 2010 after 12 years and a cost of some $300 million.

It found that unjustified firing by British soldiers caused the deaths and that none of the dead had posed a threat at the Bogside on January 30th, 1972, when parachute regiment troops opened fire during a civil rights march.

PSNI Chief Constable Baggott explained: “It’s going to be a lengthy investigation. This has to be done to modern standards of murder investigation which is both resource-intensive and prolonged.

“We understand fully our legal obligations and are committed to doing this.”

“Firstly, I need to bring a conversation with the policing board in October in order to work through the implications and the consequences.”

Campaigner John Kelly, whose 17-year-old brother Michael was one of the victims, told local media of his hope that prosecution would come soon.

He said: “The Saville report was totally damning of the troops and found that they unjustifiably murdered our people.

“It shouldn’t take much longer to come to the point where these guys should be prosecuted for what they did.”

Northern Ireland assembly member Gerry Kelly said: “I want to know when the police would move ahead with the investigation.

“This is a huge issue. People have waited a long time for justice in terms of this.”