The Internal Revenue Service’s manual reportedly used to contain instructions on how IRS agents could use information from a special Drug Enforcement Administration program as tips, but would then need to cover up the original source of the information by developing independent evidence if any of it were used in affidavits, court proceedings or investigative files.

Reuters reported Wednesday that the Internal Revenue Manual contained an entry in 2005 and 2006 telling IRS agents to omit any reference to the DEA’s Special Operations Division in their files. The IRS could use the tips initially, which in some cases might come from classified sources such as National Security Agency intercepts and drug informants, but they were then required to develop independent sources of information to conceal the original investigative trail by developing their own sources of evidence, such as surveillance, wiretaps and their own confidential sources.

“Special Operations Division has the ability to collect, collate, analyze, evaluate, and disseminate information and intelligence derived from worldwide multi-agency sources, including classified projects,” said the IRS manual in 2005 and 2006, which removed the reference in 2007. “SOD converts extremely sensitive information into usable leads and tips which are then passed to the field offices for real-time enforcement activity against major international drug trafficking organizations.”

The IRS document said the DEA’s SOD information could only be used for drug investigations, although DEA officials told Reuters that the SOD’s role has since expanded to other areas of organized crime enforcements such as money laundering.

IRS agents were instructed to use the tips to find new, “independent” evidence so as not to reveal the original confidential source.

“Usable information regarding these leads must be developed from such independent sources as investigative files, subscriber and toll requests, physical surveillance, wire intercepts, and confidential source information,” said the manual. “Information obtained from SOD in response to a search or query request cannot be used directly in any investigation (i.e. cannot be used in affidavits, court proceedings or maintained in investigative files).”