Senior commanders from the Police Service of Northern Ireland have briefed relatives of the 14 people who died after British Paratroopers opened fire on civil rights demonstrators in the city.
Police had earlier signalled their intent to investigate Bloody Sunday after they and prosecutors reviewed the findings of the Saville public inquiry into the controversial shootings.
Lord Saville found the killings were unjustified and none of the dead posed a threat.
That contradicted the long-standing official version of events, from the contentious 1972 Widgery report, which exonerated the soldiers.
The inquiry prompted PM David Cameron to apologise to the relatives.
Separately, Northern Ireland's Police Ombudsman is to launch a fresh investigation into the loyalist gun massacre at Loughinisland in 1994.
Dr Michael Maguire's inquiry comes after families of the six men killed criticised his predecessor's report.