Switzerland has hit back at being officially blamed for Italy's nationwide power blackout - and says more cuts are inevitable.
The blackouts lasted up to 18 hours
An initial European report blamed Swiss errors after a tree hit a power line.
But a separate inquiry by the Swiss energy department accuses Italy of exceeding agreed levels of imports - sometimes by "enormous" amounts.
And it says unless international laws on the issue are improved, further power cuts will happen.
"There is clearly a need for binding regulations," the department said.
EU-wide standards on cross-border electricity trading are due to come into effect next July, and the Swiss report says they are vital for Switzerland too.
"It will only be possible to prevent blackouts of the kinds that occurred on 28 September if these regulations are
implemented in an effective manner throughout Europe," it says.
While accepting some Swiss blame, it says the Italian practice is overburdening power grids in the Alps and had being going on for some time.
"The chronic gaps are the product of decisions by Italian and French network operators and of their respective regulatory
authorities," said a statement from the department.
"The deep causes of the blackout are to be found in the persistent incompatibility between the commercial interests of the countries and companies concerned on one side, and the legal and technical constraints that allow the secure use of the network on the other hand," the statement said.
COUNTDOWN TO BLACKOUT
0301: Tree hits Mettlen-Lavorgo line
0311: Etrans calls Rome power centre of Italian grid operator GRTN to lower power imports
0321: GRTN's lower power imports comes into effect
0325: Sils-Soazza line also tripped after it is hit by tree
0330: Power blackout hits Italy
The original report, The Union for the Co-ordination of Transmission of Electricity (Ucte), said Swiss power operator Etrans failed to react quickly enough as the chain of events leading to the power cut unfolded.
But the Swiss report dismissed that finding - blaming a slow response on the Italian side of the border.
"The reaction on the Italian side was late and had too little effect," Swiss statement said.
The power cut left thousands of Italians trapped on trains, in lifts and on underground services.
When the power cut happened, Switzerland was supplying 550 megawatts more power to Italy than had been agreed, while France was supplying 438 megawatts less than agreed, the Swiss report says.
The sequence of events began when first one tree and then another hit power lines in during a storm.
The Ucte report said the blackout could have been avoided if staff at Etrans had taken more effective action in the 30 minutes between the two power-line failures.