(Combines stories, adds details)
* Euribor compiler says too many banks involved to manipulate
FRANKFURT/BRUSSELS, Oct 19 (Reuters) - Deutsche Bank's <DBKGn.DE> London offices were among those raided as part of a European Commission investigation into whether Euribor, the interbank euro lending rate, has been manipulated, a person familiar with the matter said.
The Commission confirmed on Wednesday it had seized documents from institutions active in financial derivative products linked to Euribor because of concerns they may have violated European Union antitrust rules.
The Commission, which acts as an antitrust regulator in the 27-state EU, did not identify the companies or the member countries where it had carried out the raids.
However, one source familiar with the matter said Germany's largest bank had been targeted. Deutsche Bank declined to comment.
Euribor, which is set by 44 banks, is used to benchmark interest rates on trillions of euros worth of euro-denominated loans and debt instruments.
The move by European officials marks an escalation of a global investigation by enforcement agencies in the United States, Europe and Japan into whether Libor (the London Interbank Offered Rate) was manipulated during the last financial crisis.
Euribor-EBF, which compiles the Euribor benchmark, said it would share data with authorities and insisted it would be impossible for banks to fix Euribor because of the sheer number of institutions involved in setting the rate.
"We are fully confident in the governance of Euribor. With so many banks involved in setting the rate, fixing a rate artificially would be impossible," said Cedric Quemener, manager of Euribor-EBF, which compiles the benchmark.
"I believe the Commission lacks knowledge about how those benchmarks are made. We are ready to help them," he told Reuters. (Reporting by Alexander Huebner in Frankfurt, John O'Donnell in Brussels; Editing by Ludwig Burger and Will Waterman)