Congressional hearings have revealed confusion by power operators in the blackout that hit 50 million Americans and Canadians last month.
The blackouts caused huge disruption
The revelations came as the House Energy and Commerce Committee concluded a two day hearing into the power outage, with Ohio energy company FirstEnergy under fire as the leading candidate to take the blame.
The committee released a transcript of a conversation between FirstEnergy's control room and the Midwest power grid hours before the system collapsed.
The FirstEnergy operator said: "We have no clue. Our computer is giving us fits. We don't even know the status of some of the stuff around us."
FirstEnergy's chief executive Peter Burg has denied wrongdoing.
"Events in our system, in and of themselves, could not account for the widespread nature of the outage," he told the committee.
However, Committee chairman Representative Billy Tauzin said the transcripts were "disturbing" and showed "a lot of confusion by people who were supposed to be in the know".
Congressional leaders from the House and Senate will meet on Thursday to discuss plans for a wide-ranging energy bill, which will now include a mandatory grid reliability provision along with measures to boost oil and gas production and encourage the building of more power plants.
They are hoping to introduce a bill by 1 October.
About 50 million people in eight north-eastern US states and the Canadian province of Ontario suffered the massive blackout last month, which took down several regional power grids.
The power outage caused widespread disruption, with thousands of people on the New York subway trapped, factories closed and hundreds of flights cancelled.
A series of failures in four transmission lines - three of them owned by FirstEnergy - have come under suspicion as the power failure's possible starting point.
Other power operators questioned why FirstEnergy had been so slow in telling operators of the problems.
They pointed to the other Ohio utility American Electric Power, which had managed to disconnect from the grid and suffered only limited disruption.
Michigan Democrat Bart Stupak asked why FirstEnergy did not respond in this way, and said there was a lack of corporate "responsibility or accountability when things start to go haywire".
The blackout is also the subject of a joint Canadian-American investigation which is expected to take another month before it will collect all necessary data - and perhaps a year before it will give a full report.
US Energy Secretary Spencer Abraham said it was too early to be pointing the finger of blame.
Speculation was "premature" he said. "We won't jump to conclusions. Our investigation will be thorough and objective."
He added that the US-Canadian inquiry would "follow the facts wherever they lead us".