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Related Links Document: Reports on Credit Suisse

LONDON – Credit Suisse on Thursday became the latest big financial institution to confirm that it was facing regulatory inquiries over its private stock trading platform, known as a dark pool.

Credit Suisse, one of the largest dark pool operators, is also among more than 30 defendants in lawsuits over high-frequency trading pending in Federal District Court in New York.

This week, UBS, a Swiss rival, and Deutsche Bank of Germany acknowledged that they were facing inquiries from regulators.

The disclosures come after New York’s attorney general, Eric T. Schneiderman, sued Barclays in June, accusing the British bank of favoring high-frequency traders over other investors in the Barclays LX dark pool. Barclays has asked that the suit to be dismissed.

“Credit Suisse is responding to inquiries from various governmental and regulatory authorities concerning the operation of its alternative trading systems, and is cooperating with those requests,” the Swiss bank said on Thursday.

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On Tuesday, UBS said it had received inquiries about its own dark pool, or alternative trading system, and its order routing and execution practices. The inquires were made by the Securities and Exchange Commission, the New York attorney general and other regulators as part of an industrywide investigation.

Deutsche Bank separately disclosed on Tuesday that it had received inquiries from regulators related to high-frequency trading, but did not disclose the regulators.

Mr. Schneiderman’s office has made inquiries to Deutsche Bank on issues related to its dark pool and high-frequency trading, according to a person briefed on the matter, and is said to be looking at Credit Suisse over dark pools.

UBS and Deutsche Bank have both said they are cooperating in the inquiries.

Dark pools have grown in popularity in recent years, in part because they allow large investors like pension funds to place orders privately, without alerting the rest of the market to their actions.