The European Commission raided the offices of nine mobile phone companies in the UK and Germany yesterday to investigate possible price-fixing on roaming charges.
Further raids on other European mobile operators, including Eircell and Digifone in the Republic, were not ruled out last night by a Commission spokesman.
The UK and German raids were part of an inquiry which is looking for evidence of "collective fixing of consumer retail prices by mobile operators in both countries".
This follows an earlier two-year, European-wide investigation into roaming rates - the charges travellers pay when they make a mobile call in a foreign country.
These charges mean European travellers can pay more than 10 times as much to make a mobile call in Europe than their counterparts in the US.
A Commission statement said it was also looking for evidence "to verify whether German operators have illegally fixed the wholesale prices they charge".
Several mobile operators in Britain, including Vodafone and BT Cellnet, confirmed the visits by the European Commission, accompanied by representatives from Britain's Office of Fair Trading.
In Germany, Deutsche Telekom said its corporate headquarters and its T-Mobile unit had both been searched. E-Plus, owned by Dutch telecoms operator KPN, also said its offices had been searched.
News of the raids prompted a fall in the share prices of mobile telephone companies, with Vodafone alone down 5.7 per cent.
Telecoms experts said they were not surprised by the Commission's intervention.
Mr Enda Hardiman, director of Dublin-based Hardiman Communications, said roaming rates were very high and had enabled operators to make huge profits.
"Competition has not been very effective in the area," he said. "There has been little impetus for operators to drive down costs."
He said it was possible raids could also be mounted in Ireland as Irish operators also agreed roaming rates through a series of bilateral negotiations with operators.
A Commission spokesman told The Irish Times last night the raids had been restricted to the UK and Germany due to the limited resources available and because roaming rates were particularly high there.
He said the inquiry was still at an early stage and when asked about the possibility of raids in other countries he replied: "nothing can be excluded."
A spokesman for Eircell - which is owned by Vodafone - said there was little "likelihood" of similar raids in the Republic. He said there was no question of collusion in roaming within the Irish marketplace and Eircell's rates compared favourably across Europe.
A spokeswoman for Esat Digifone, which is owned by BT, declined to comment.
A spokeswoman for the telecoms regulator said last night her office would aim to be as helpful as possible to the Commission.
"The Independent Regulators Group recently wrote to the Commission as to how it can help on the roaming issue," she said.