A group representing President Donald Trump's transition team is pressing the General Services Administration to turn over a memo purportedly sent by an agency official to special counsel Robert Mueller's team that would offer proof that tens of thousands of emails should not have been delivered to investigators.

The transition group, Trump for America, claims in a letter sent Monday to GSA officials that an agency memo supposedly sent last June to Mueller's team provides evidence that the emails later handed over to Mueller's investigators were legally owned by the transition. The vast cache of emails should never have been delivered to the Russia election meddling investigators without Trump for America's authorization, a lawyer for the transition group wrote in the letter obtained Wednesday by The Associated Press.

The transition lawyer, Kory Langhofer, did not explain how the group was made aware that the GSA memo exists but said "it is our understanding" that the document was sent in June by the GSA's top lawyer, Richard Beckler, to Mueller's team. Beckler has since died. Langhofer's letter to the GSA requested the memo under the Freedom of Information Act.

Get Breaking News Delivered to Your Inbox

"The GSA had no right to access or control the records but was simply serving as Trump for America's records custodian," Langhofer wrote. He added that the GSA "unlawfully" handed over "thousands of private and privileged (presidential transition team) emails to the Special Counsel's office, and failed to notify (Trump for America) of the production."

GSA spokeswoman Pamela Dixon declined Wednesday to comment on the transition group's letter. Peter Carr, spokesman for the special counsel, also declined to comment, citing an earlier statement that when the counsel's office obtains emails during its investigations "we have secured either the account owner's consent or appropriate criminal process."

Ken Nahigian, Trump for America's executive director, said the transition made the records request to the GSA to respond to the agency's role in the "unlawful seizure of Transition documents by Mr. Mueller."

Nahigian said the agency's cooperation with the special counsel without the knowledge of the transition "will irreversibly chill the operations of future presidential transition teams."

The GSA has typically provided office space, phones and computers to presidential transition teams in recent years After Trump's presidential election victory in November 2016, his transition officials relied on the federal agency's site to host and archive its electronic communications. The transition's emails were slated for deletion after Trump's inauguration, but the transition asked the GSA to retain the records after receiving document requests from Congress last spring.

Some criminal law experts have expressed skepticism about the transition's claims to legal ownership of the emails, but Langhofer and other transition officials insist that Beckler had agreed with Trump for America both in phone conversations and in the sought-after memo that the emails belonged to the transition.

Langhofer said that Beckler "acknowledged unequivocally" that the transition team "owned and controlled" the emails and that "the GSA had no right to access or control the records but was simply serving as TFA's records custodian." In Beckler's absence last August, his deputy, Lenny Loewentritt, made the decision to turn over the trove of transition emails to Mueller's team — without notifying Trump for America, Langhofer said.

Langhofer said that the memo purportedly sent by Beckler would show that the GSA "covered up" Loewentritt's "unlawfulness" in giving the transition emails to the special counsel. Loewentritt told Buzzfeed last month that Beckler had made no commitment to transition officials that requests from law enforcement for materials would be routed through Trump for America. He also said there was no expectation of privacy for the transition emails.

In September, investigators for Mueller obtained tens of thousands of emails that related to 13 senior Trump transition officials. Among them was former national security adviser Michael Flynn, who pleaded guilty to one count of making false statements to FBI agents in January and is now cooperating with Mueller's investigation. Flynn was fired by Trump in February for misleading senior administration officials about his contacts with Russia's ambassador to the U.S.

Mueller so far has indicted two other Trump campaign officials and a fourth has pleaded guilty to lying to the FBI.