LONDON (Bloomberg) — Spanish police arrested six people tied to a $600 million fraud committed at Langbar International Ltd., a Bermuda-based investment company that has been under investigation in the UK since 2005.

The arrests followed a request by British authorities investigating several individuals and companies, the police said yesterday in an e-mailed statement. The arrests are connected to Langbar, according to the company's external spokesman, Andrew Benbow, and the UK's Serious Fraud Office.

Langbar, previously known as Crown Corp., operated as a "cash shell" listed on a London exchange. The company said in 2005 that it was the victim of a fraud after discovering £370 million ($530 million) missing from its accounts. In civil lawsuits, lawyers for the company called it "the largest fraud ever perpetrated on the Alternative Investment Market".

"The present board of Langbar International is determined to discover exactly what has transpired concerning company funds and to pursue their recovery," the company said on its website. "Our aim is to restore value for shareholders to the maximum that can be achieved."

The fraud dates back to 2003, when the suspects allegedly attracted investors through false claims about the company's assets, police said. Once the shares rose, the suspects sold their holdings, according to the Spanish police.

The company suspended trading two years later after failing to confirm the ownership of £370 million in deposits with two lenders, the Spanish police said. At the time of its market debut, the company claimed it held 219 million euros ($290.2 million), according to the statement.

The Spanish police, with City of London police and SFO investigators, last week arrested six men ranging in age between 56 and 76 at residences in Madrid, Barcelona and Alicante, the SFO said in its statement. Five are Spanish citizens, one is Argentine, it said. Neither the SFO or Spanish police identified the suspects.

El Pais reported that the six men were charged and released and that one of the suspects was a former Israeli Mossad agent.