WASHINGTON — Criminals used an online service run by the IRS to access personal tax information from more than 100,000 taxpayers, part an elaborate scheme to steal identities and claim fraudulent tax refunds, the IRS said.

The thieves accessed a system called “Get Transcript,” where taxpayers can get tax returns and other filings from previous years. In order to access the information, the thieves cleared a security screen that required knowledge about the taxpayer, including Social Security number, date of birth, tax filing status and street address.

The IRS said the thieves targeted the system from February to mid-May. The service has been temporarily shut down. While the system is shut down, taxpayers can still apply for transcripts by mail.