Story highlights The transition maintains the documents were its property and should not have been handed over without its approval

The emails in question involve 13 transition officials, including four senior ones, according to the letter

Washington (CNN) A spokesman for special counsel Robert Mueller has denied accusations by Trump transition lawyers that Mueller's team got unauthorized access to thousands of transition emails.

"When we have obtained emails in the course of our ongoing criminal investigation, we have secured either the account owner's consent or appropriate criminal process," the spokesman, Peter Carr, said early Sunday.

Lawyers representing the transition wrote to members of Congress accusing Mueller's team of obtaining unauthorized access to tens of thousands of transition emails in the course of its Russia investigation, including what they claim to be documents protected by attorney-client privilege.

The transition maintains the emails, which were on a government domain, were its property and should not have been handed over without its approval. The emails in question involve 13 transition officials, including four senior ones, according to the letter.

The lawyer, Kory Langhofer, wrote to leaders of the Senate Homeland Security and House Oversight and Government Reform committees because he said the General Services Administration, which supports presidential transitions, "unlawfully produced" private materials of the transition although the GSA "did not own or control the records in question."

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