US Attorney General Merrick Garland has said he "personally approved" the search of Donald Trump's Florida home.
He stressed there was "probable cause" for the unprecedented action against the former US president.
The search was carried out amid a probe that sources have said is focused on whether Mr Trump illegally removed records from the White House as he was leaving office.
Mr Garland also said the US Justice Department had asked a court to unseal a search warrant filed as part of the investigation due to "substantial public interest" after Donald Trump himself announced what had happened in a statement on Monday night.
It was not clear whether the ex president's legal team would object to the release of the warrant, which could shed light on the nature of the investigation.
In a statement today, Mr Trump said: "My attorneys and representatives were co-operating fully and very good relationships had been established.
"The government could have had whatever they wanted, if we had it."
Mr Garland condemned "unfounded attacks" on the integrity of the US Justice Department and the FBI that erupted after the raid on Mr Trump's Mar-a-Lago home last Monday.
The dramatic raid on his palatial Florida residence has supercharged the bitter, polarising political debate around the slew of judicial investigations facing the former US president as he considers another White House run.
"Nothing like this has ever happened to a President of the United States before," the 76-year-old Mr Trump said of the day-long search of his luxury resort.
US Attorney General Merrick Garland has said the US Justice Department has filed a motion to unseal the warrant related to a search at former President Donald Trump's Mar-a-Lago resort in Florida earlier this week | Read more: https://t.co/GFbDVaQRJo pic.twitter.com/UTuNZkrY2e— RTÉ News (@rtenews) August 11, 2022
The unprecedented search at Mr Trump's Palm Beach property marked a significant escalation in one of the many probes he is facing from his time in office and in private business.
Mr Garland's Justice Department has faced fierce criticism and online threats this week following the search.
A source who had been briefed on the matter told Reuters that the Justice Department also has surveillance footage from Mar-a-Lago in its possession.
Trump supporters, and some of his fellow Republicans in Washington, have accused Democrats of weaponising the federal bureaucracy to target the former president.
The FBI said an armed person had tried to breach its office in Cincinnati early today in what it called a "critical incident."
Local law enforcement said officers traded shots with a male suspect wearing body armour.
Merrick Garland condemned the attacks on employees of the FBI and Justice Department.
"I will not stand by silently when their integrity is unfairly attacked," he said.
US Attorney General Merrick Garland has said he would not stand by silently while 'unfounded attacks' are made about the FBI and US Justice Department following a search of former President Donald Trump's Mar-a-Lago resort this week | Read more: https://t.co/GFbDVaQRJo pic.twitter.com/bKK6pf2yWd— RTÉ News (@rtenews) August 11, 2022
Some Democrats, meanwhile, have criticised Merrick Garland for being overly cautious in investigating Donald Trump over his attempts to overturn his 2020 election loss to Biden.
Republican reaction split between those ready to attack the attorney general and the FBI for the Trump search and others who warned against rhetoric that could undermine federal law enforcement.
"I have been ashamed to hear members of my party attacking the integrity of the FBI agents," Representative Liz Cheney, the Republican vice chair of the House committee investigating the 6 January attack on the US Capitol wrote on Twitter.
"These are sickening comments that put the lives of patriotic public servants at risk."
But Republican Senator John Cornyn mocked Mr Garland for suggesting the search could have been conducted quietly.
"Who would possibly believe that an application and issuance of search warrant for a former President's home and subsequent search could be done 'quietly?'" the Texas Republican asked on Twitter