The company reported record profits in 2007, and has won a new army supply contract for the Middle East.
KBR said in a statement to Al Jazeera on Monday that the witnesses tesfiying on Monday's hearing "have raised claims that KBR has previously addressed".
"The government has reviewed these claims and refused to join lawsuits asserting them," it added.
'Not interested'
Republicans have blocked Democrats' efforts to set up a congressional committee with the legal authority to investigate war profiteering.
But Pratap Chatterjee, a director of global corporation watchdog Corpwatch, told Al Jazeera on Sunday that "Americans are not interested" in the hearings.
"The hearings are about, 'are our troops getting good enough care'?" he said.
Although the US justice department has prosecuted several former KBR employees for corruption and the company has refunded some money from overcharging, the government has not charged the company with any criminal offences.
But Corpwatch's Chatterjee said "as opposed to companies profiteering from soldiers, the US is spending what it takes to keep its soldiers there".
It was the US military that "encourages KBR to spend as much as possible to make the soldiers happy, to make them comfortable", he said.
"It's a culture of excess there - the way the soldiers are fed and treated. If you go to the big bases it looks like a 50s movie set."