BERLIN - A German electric company said Sunday a high-voltage transmission line it shut down over a river to let a ship pass could have caused the chain-reaction power outages that left about 10 million people in the dark across Europe.

The blackouts Saturday night briefly halted trains in Germany and trapped dozens of people in elevators in France and Italy. Austria, Belgium and Spain were also affected, though supplies to most regions were quickly restored. No injuries were reported.

Sun rises over a frozen field near Hanover. A surge in electricity demand in Germany due to cold weather triggered blackouts across western Europe, leaving about 10 percent of French consumers without power, electricity operators said. [AFP]

The outages raised fresh questions about the reliability of Europe's interconnected power grids and drew an immediate call for stronger coordination.

A private German company, E.On AG, said the problems began in northwestern Germany, where its network became overloaded possibly because it shut down the transmission line over the river. The company said it had shut down transmission lines in the past without causing problems, and it was still investigating what happened this time.

Theo Horstmann, a spokesman for another German power firm RWE AG, said the shortage caused substations across Europe to close down automatically to maintain supplies elsewhere.

Swaths of western Germany, including the industrial Ruhr region, were without power for a half hour, delaying scores of trains for up to two hours, said Achim Stauss, spokesman for rail operator Deutsche Bahn.

Officials said thousands of worried people overwhelmed emergency services with telephone calls.

French power distributor RTE said the problems in Germany caused a "brutal imbalance" in supply and demand of electricity across the continent.

"Such imbalances must be corrected immediately to avoid a complete meltdown of the European electric system," the company said in a statement.

As a result, RTE shut off supplies to some 5 million people across most regions of the country, including parts of Paris, for about a half hour.

The company estimated that 10 million people were affected in all Europe.

The German government demanded a quick explanation from Essen-based E.On of what happened ¡ª and of how it will prevent any reoccurrence.

"Power outages of this kind are not only annoying for people, but also represent a considerable risk for the economy," said Economy Minister Michael Glos.

Horstmann said the network's safety mechanisms functioned perfectly, heading off a dangerous drop in the frequency of power supplies.

RTE President Andre Merlin also insisted that Europe's power network had worked smoothly.

"Despite the outages, we were able to avoid a total blackout yesterday," he told reporters on a conference call Sunday.

However, Italian Prime Minister Romano Prodi said the incident suggested Europe needed to strengthen its coordination of power supplies.

"My first impression is that there is a contradiction between having European (power) links and not having one European (power) authority," Prodi told reporters in his home town of Bologna. "We depend on each other with being able to help each other, without a central authority."

Italy was the victim of Europe's last major power outage in 2003, when a short in a power line in Switzerland started a chain reaction that left 95 percent of Italy's population in darkness for several hours.

A similar incident occurred in the United States in 2003, when tree limbs touching a power line in Ohio triggered a blackout that cascaded across the eastern part of the country and into Canada, affecting 50 million people.