AFP - Three top executives of French engineering group Alstom in Britain were freed Wednesday without charge after having been arrested for alleged bribery and corruption, the firm and investigators said.

The president, legal director and finance director of the firm's British branch were released after being detained in raids across the country, company spokesman Patrick Bessy told AFP.

The firm said in a statement on its website that "several Alstom offices in (Britain) have been raided on Wednesday," adding that those detained "were freed late afternoon without being charged."

The arrests were related to a Swiss investigation into bribery allegations that had been going on for more than three years, said the group.

"They have been released on police bail. They have not been charged," said a spokesman from Britain's Serious Fraud Office (SFO) which is leading the probe here.

The executives were detained in dawn raids at nine locations across Britain involving more than 150 police and anti-fraud investigators and spent the day being interviewed at police stations, said the SFO in a statement.

They were arrested during the raids at five Alstom business addresses and four residential premises in central and northeast England and London.

"Three members of the board of Alstom in the UK have been arrested on suspicion of bribery and corruption, conspiracy to pay bribes, money laundering and false accounting," according to the SFO.

The raids were part of an SFO investigation code-named Operation Ruthenium into "the suspected payment of bribes by companies within the Alstom group in the UK."

"It is suspected that bribes have been paid in order to win contracts overseas, and that this has involved associated money laundering and other offences," the SFO said.

Alstom said in a statement the firm had been under investigation "by the Swiss justice for more than three years on the motive of alleged bribery issues.

"Within this frame, Alstom?s offices in Switzerland and France have already been searched in the past years.

"Alstom is cooperating with the British authorities."

The SFO said it had been working closely with Swiss police and legal authorities and a number of police forces across Britain.

"The SFO is committed to tackling corruption," said SFO chief Richard Alderman.

"We are working closely with other criminal justice organisations across the world and are taking steps to encourage companies to report any suspicions of corruption, either within their own business or by other companies or individuals."

French engineering group Alstom specialises in infrastructure projects in the electricity production and rail sectors. It has offices in 70 countries with more than 80,000 employees.