By Jonathan Beale
BBC News, Washington
Blackwater is accused of the unjustified killing of Iraqi civilians
The killings of at least 14 Iraqi civilians by guards from the security firm Blackwater were unjustified, FBI officials have told the New York Times.
The officials are investigating the 16 September incident in which 17 Iraqis were shot by Blackwater staff guarding State Department employees.
The revelations come as the US State Department's inspector-general admits his brother is linked to Blackwater.
The official admitted the link while giving evidence to Congress.
Members of Congress are conducting an investigation into the activities of private security firms like Blackwater.
The State Department's inspector-general, Howard Krongard, was the latest senior official called to give evidence on Capitol Hill.
Mr Krongard is responsible for State Department contracts and ensuring that the department behaves ethically.
At the start of the hearing, he wanted to quash what he called ugly rumours that his own family was linked to Blackwater.
He said his brother had no financial relationship with the private security firm.
But after a break in proceedings, his testimony dramatically changed.
"During the break, I did contact my brother... I learned that he had been at the [Blackwater] advisory board meeting yesterday," he said.
"I had not been aware of that and I want to state it on the record right now that I hereby recuse myself from any matters having to do with Blackwater."
That astounding revelation prompted only more questions as to why Mr Krongard had not previously established his brother's links to Blackwater, especially in the wake of the September 16 shootings that first put Blackwater under the spotlight.
The New York Times, quoting unnamed US officials, says a preliminary FBI investigation has found that at least 14 of the 17 shootings that day were unjustified and violated Blackwater's rules of engagement.
Blackwater still insists its employees came under attack before opening fire.
The FBI investigation is ongoing, but the State Department's links to Blackwater have already proved damaging.