(CNN) Special counsel Robert Mueller has issued a subpoena to the Trump campaign for more Russia-related documents, two sources familiar with the matter tell CNN.

The special counsel had previously received the information that had already been handed over to Congress, but investigators felt there were things they didn't see. The new subpoena seeks more records based on various search terms.

One source described it as a "cleanup" subpoena, expanding the search terms. The campaign is in the process of complying, the source said.

The White House has not received a similar subpoena, CNN is told.

Read More