Shares in online gambling groups fell in London yesterday after David Carruthers, chief executive of UK-listed BetonSports, was detained in the US.
Shares in the online gaming group fell 17 per cent to 122p. Meanwhile, 888 Holdings shares were down 3.5 per cent at 193p, Sportingbet fell 13 per cent to 282p, and the largest online poker group, PartyGaming, fell nearly 6 per cent to 103p.
BetonSports said no one from the company had been able to talk to Mr Carruthers since his detention on Sunday night.
Mr Carruthers and his wife were en route from the UK to the BetonSports headquarters in Costa Rica when federal authorities approached him in the transit lounge of a US airport.
His wife was allowed to continue the flight to Costa Rica.
Other internet gaming companies whose share prices have been affected by the detention of Mr Carruthers, including PartyGaming, had been in contact with BetonSports seeking information.
The company said: "The board is currently seeking clarification as to the basis of the detention and a further announcement will be made when appropriate.
"The business continues to trade normally. In particular, the Antigua-licensed gaming activities serviced in Costa Rica and Kuala Lumpur are operating as usual."
Mr Carruthers was in the UK for last Friday's BetonSports annual meeting.
Online gambling has grown into a $12 billion (€9.6 billion) worldwide industry. Half of the revenues are made in the US, but none of the world's 2,500 gambling sites are based there.
The 1961 Interstate Wire Act bans gambling over the telephone and, according to the US department of justice, over the internet as well, although this has not been tested in court.
Last week, the House of Representatives voted to criminalise electronic payment to gambling sites whether by credit card, wire transfer, debit or "e-wallet".
The Goodlatte/Leach Bill makes it illegal for US financial institutions to transfer money to offshore gambling websites or to the online payment services those sites use. But it allows online bets on horse races, as well as internet-based state lotteries.
However, analysts believe the Bill will not make it into law because a lack of time means it is unlikely to be passed by the Senate.
Bob Goodlatte, a House Republican sponsor of the Bill, blamed online betting for "moral decline". Jon Kyl, a Republican senator, said internet gambling was "as perniciously addictive as crack cocaine". But Barney Frank, a Democratic congressman, said: "Prohibition didn't work for alcohol, and it won't work for gambling."
Last week, Mr Carruthers said the Senate had no appetite to discuss the Bill. He added that the debate on internet gambling was moving in the company's favour and that the chances of the Senate backing the Bill to outlaw internet gambling in the US were "remote".
Mr Carruthers worked for Ladbrokes for 24 years before joining BetonSports.
