Energy experts from the EU are holding emergency talks on Wednesday on the crisis caused by the row between Russia and Ukraine over the price of gas.
Russia says gas supplies to Europe have now been fully restored
Officials from the 25 member states will examine the extent to which they were affected when Russia stopped pumping gas to Ukraine on Sunday.
The talks come hours after Russian and Ukrainian officials met to seek a solution to the stand-off.
Kiev has refused to accept Russia's proposed four-fold price increase.
Several countries reported shortfalls in the gas flow on Monday and the European energy commissioner, Andris Piebalgs, said the situation showed how vulnerable the EU was to shortages.
The Russian energy company, Gazprom, said gas supplies to central and western Europe were fully restored on Tuesday.
Poland says it is looking for alternatives to Russian energy supplies. Hungary described energy as a security issue, while Austria said Europe needed a long-term strategy to secure supplies.
Wednesday's meeting, at 0930 local time (0830 GMT), will be to gather information on how badly affected EU member states were before Russia promised to restore full delivery to Europe.
Officials at the European Commission are pushing for more powers to compel member states to hold reserves of gas - and if necessary to sell them to other countries.
A similar initiative just over three years ago was, in the words of one senior official, "cut to shreds" by the member states.
BBC Europe correspondent Tim Franks in Brussels says that what Europe should do about its energy supply could be one of the big political questions of 2006.
While there is relief that no European customer was cut off, there has been a surge of concern, he says, with parts of the continent heavily reliant on Russian gas.
"The situation has shown how vulnerable the union is to shortages of gas supply," Mr Piebalgs said.
Gazprom stopped exporting gas to Ukraine on Sunday, after Ukraine refused to accept a rise in price from $50 to $230 for 1,000 cubic metres, but left enough in the pipeline for other customers.
The company has repeated claims that Kiev is stealing gas intended for Europe.
Ukraine says it is only taking gas it bought from Turkmenistan, from the pipelines crossing its territory.
However, Russian Industry and Energy Minister Viktor Khristenko said Russia was now buying all the Turkmen gas that entered the pipelines leading from Russia to Ukraine.
Kiev says it is being punished for its attempts to become more independent from Moscow and develop stronger ties with the West.
Gazprom is still charging low prices to some former Soviet countries, and has said it would give the same preferential treatment to Ukraine if it gave Russia control of the export pipeline.
Moldova says it was also cut off after refusing to double what it paid to $160 for 1,000 cubic metres.