Washington (CNN) - The Internal Revenue Service has told House GOP investigators they have identified 88 IRS employees who may have documents relevant to the congressional investigation into targeting of conservative groups, according to a congressional source familiar with the investigation.

The IRS asked these employees to preserve all the "responsive documents" on their computers, and it has been in the process of collecting it all to comply with congressional requests for information. The IRS missed its May 21st deadline to turn over documents to the House Ways and Means Committee.

The same source said the IRS argues it missed its deadline because of the scope of documents it is collecting.

The request for documents was a bipartisan one, but Republicans are privately preparing to seize on the fact that if nearly 90 IRS employees may have been somehow involved in this targeting, it is evidence that the controversy extends well beyond the mistakes by a few low level employees.

However, with no documents in hand, there is no way to know how many of the employees being asked to preserve documents were truly involved in the activity in question. The IRS, in a statement to CNN, said the large number reflects its effort to ensure they are as responsive as possible to the Congressional requests.

"The IRS and Acting Commissioner Danny Werfel are moving aggressively and taking the data requests very seriously. As a precautionary measure, the IRS is casting a wide net to capture any potentially related materials. Our goal is to be exceedingly thorough during this process to ensure we identify any and all pertinent records," the IRS statement said. "The IRS has received numerous congressional requests involving an extensive set of questions and calls for data. Responding to these requests is a top priority for us. We have been in contact with committee staff, and we continue to provide them updates as we diligently work through these requests."

The IRS is responding to multiple Congressional requests for information and struggling to meet the deadlines. According to a Senate Finance Committee aide, the IRS told the committee it will also miss Friday's deadline to produce documents relevant to the tea party targeting.

In a joint statement from the press offices of Sens. Max Baucus and Orrin Hatch, the committee's Democratic chairman and its top Republican, said they were disappointed and that the agency needed to do better.

"This is an agency that revolves around making the American taxpayer meet hard deadlines each and every year when they file their taxes, oftentimes penalizing those that are late," the statement said.

More problems are on the horizon for the IRS. Rep. Darrell Issa, who chairs the House Oversight and Government Reform Committee, will hold a hearing next week on an audit of the agency's "spending culture and conference abuses."

The committee will focus on the report released by the Treasury Inspector General for Tax Administration (TIGTA) that shows excessive spending at IRS conferences.

Werfel said in a statement that the report will focus on an IRS conference that took place in 2010 and labeled it an "unfortunate vestige from a prior era."

"While there were legitimate reasons for holding the meeting, many of the expenses associated with it were inappropriate and should not have occurred," he said, adding new rules have been put in place and such a conference will not happen under his watch.