ROME -- The Italian government has announced a rapid and radical overhaul of its electricity sector after a weekend blackout left most of the country without power for many hours.

As engineers nursed the nation's network back to full capacity, magistrates opened an investigation into the outage — the latest power failure to have snarled a major Western economy in recent months.

And Prime Minister Silvio Berlusconi's centre-right government said it was preparing to rush into law a special blackout decree to clear the way for the swift construction of new power stations.

Giampaolo Bettamio, a government expert preparing the legislation, said the government would also shake up the domestic electricity market, giving state-controlled energy groups Eni and Enel one year to sell off their gas and electricity distribution networks, which control the market.

Industry Minister Antonio Marzano will address parliament today about the crisis, which was the biggest outage Italy has suffered since the power system was nationalized in the 1960s.

"The blackout ... must not become a metaphor for a country which is sliding toward chronic delays," Pier Ferdinando Casini, a senior coalition partner and Speaker of the lower house of parliament, told the newspaper Corriere della Sera.

The government decree will aim to sidestep the red tape and open the way for a huge building program.

Marzano hopes the liberalization of the transmission market will encourage much-needed foreign investment and know-how into the sector.

The trigger for Sunday's blackout appeared to have been a tree falling into a major Swiss line carrying power to neighbouring Italy — which could have caused over-capacity on French lines to Italy, resulting in a domino-like collapse.

However, Swiss officials said Italy had been too slow to respond to warnings about the problem and politicians complained that years of underinvestment had left the country woefully reliant on electricity imports.

Electricity was restored quickly in the north, but Rome had to wait for 12 hours to get its lights back and parts of the south were without electricity until recently.