new york (Bloomberg) — The Justice Department is conducting a criminal investigation of HSBC Holdings Plc clients who may have failed to disclose accounts in India or Singapore to the Internal Revenue Service, according to three people familiar with the matter.

One client got a letter from the Justice Department in late June that said prosecutors had "reason to believe that you had an interest in a financial account in India that was not reported to the IRS on either a tax return" or a Treasury Department report disclosing foreign accounts, according to a copy read to Bloomberg News by a lawyer for one of the clients.

"This is a global initiative by IRS and the Department of Justice," said Robert McKenzie, an attorney at Arnstein & Lehr in Chicago who said he spoke to two people who got letters.

The probes show how the US is expanding its crackdown on offshore tax evasion beyond Switzerland and UBS AG, the largest Swiss bank, said Barbara Kaplan, a tax lawyer at Greenberg Traurig LLP in New York. London-based HSBC is Europe's biggest lender by market value.

"It's clear that the IRS and the Department of Justice are intending to pursue other depositors outside of Switzerland," Kaplan said. "They've announced it before, and they are moving forward in that regard."

The letters could mean that prosecutors got data on HSBC account holders from the bank, McKenzie said.

"My speculation is that there has to be some level of cooperation within HSBC, or someone within HSBC providing these names to the government," McKenzie said. "I would bet, under pressure, HSBC cooperated."

HSBC spokeswoman Diane Bergan declined to comment.

UBS avoided prosecution last year by admitting it aided tax evasion from 2000 to 2007, paying $780 million, and agreeing to disclose secret account data on more than 250 clients. It later agreed to disclose data on another 4,450 clients.

Seventeen UBS clients, two bankers and three alleged enablers of tax crimes have been prosecuted since the bank signed the deferred prosecution agreement. Another 15,000 US residents sought to avoid prosecutions last year by disclosing offshore accounts.

IRS Commissioner Douglas Shulman said last October his agency was scouring those disclosures "to identify financial institutions, advisers and others" who helped taxpayers cheat on taxes. He said the IRS is hiring 800 people in the next year and increasing staff in eight overseas offices, including Hong Kong. It also will open offices in Beijing, Sydney and Panama City.

The letters don't mention HSBC by name yet are all directed to people with accounts at the bank, according to lawyers who saw them. About a dozen HSBC clients got letters in late June from Kevin Downing, a senior attorney in the Justice Department's tax division who led the UBS probe, according to the people.

Tax attorney Larry Campagna said that prosecutors often give taxpayers a chance to explain their accounts to the Justice Department. Campagna represents clients of banks in the offshore tax investigation and hasn't seen the letters.

Sometimes such letters lead to a guilty plea, and sometimes there's an explanation that causes a prosecution to drop the investigation, said Campagna of Chamberlain Hrdlicka in Houston.

The letters went to US residents who have ties to India, including people who inherited money from relatives or maintained assets there after leaving the country, according to three lawyers who read them and asked not to be identified. Some letters referred to undisclosed bank accounts in Singapore, two of the lawyers said.

"We've been telling our clients that the non-disclosure of foreign accounts is not just a UBS problem," said tax attorney Richard Sapinski of Sills Cummis & Gross in Newark, New Jersey, represents clients in the offshore investigation. He doesn't have a client who got a letter.

"We've spoken to the prosecutors and high-level people in the IRS, and our conclusion was they were going to pursue people with undisclosed foreign accounts anywhere for a very long time to come," he said.

Several weeks ago, Downing toured Singapore, Hong Kong and Beijing, meeting with regulators and bankers about offshore tax prosecutions. He spoke to tax lawyers at a conference sponsored by New York University on June 18.

"We just took down the largest private wealth management bank in the world," Downing said, referring to UBS. "Do you really think we're going to have trouble doing the next one?"