examination of data recordings, witness statements and available military intelligence.

Saudi intelligence has a number of informants on the ground in Yemen. So officers would have known that the funeral was also being attended by several senior Houthi rebels that Saudi Arabia is fighting, as well as allied tribal leaders.

What is not yet clear is whether the pilot took it on himself to release his bombs or whether he was ordered to do so by someone higher up the command chain.
Image copyright Reuters
Image caption The attack was widely condemned
Image copyright AFP
Image caption The Saudi-led coalition has denied responsibility for the attack

One Saudi official said there would be no public statement until the investigation was complete, a process which could take days, weeks or even months.

With casualties mounting in Yemen, the UK is under pressure to suspend its lucrative arms sales to Saudi Arabia.

Defence Secretary Sir Michael Fallon has said the government could review those sales if it is found that civilians were knowingly targeted in an air strike.