The chairman of the US House of Representatives Intelligence Committee has flatly denied Donald Trump’s claims about a wiretap on his Trump Tower residence in New York.
But, speaking at a hearing on Russia's involvement in last year’s presidential election, he said it was still possible other surveillance was used against Mr Trump.
In his opening statement, Republican Devin Nunes told the committee: "Let me be clear. We know there was not a wiretap on Trump Tower.
“However, it's still possible that other surveillance activities were used against President Trump and his associates."
The Republican also said the committee has seen no evidence to date that officials from any campaign conspired with Russian agents, but will continue to carry out investigations into the issue.
He also said the committee will investigate who has been leaking classified information about investigations into Russia's interference.
Mr Nunes said he hopes the committee's hearings will result in a “definitive report” on Russia's involvement in the presidential election.
FBI director James Comey and National Security Agency Director Michael Rogers will both testify.
The controversial orders Donald Trump has already issued
The controversial orders Donald Trump has already issued
1/9 Trump and the media
White House Press Secretary Sean Spicer takes questions during the daily press briefing
2/9 Trump and the Trans-Pacific Partnership
Union leaders applaud US President Donald Trump for signing an executive order withdrawing the US from the Trans-Pacific Partnership negotiations during a meeting in the Roosevelt Room of the White House in Washington DC. Mr Trump issued a presidential memorandum in January announcing that the US would withdraw from the trade deal
3/9 Trump and the Mexico wall
A US Border Patrol vehicle sits waiting for illegal immigrants at a fence opening near the US-Mexico border near McAllen, Texas. The number of incoming immigrants has surged ahead of the upcoming Presidential inauguration of Donald Trump, who has pledged to build a wall along the US-Mexico border. A signature campaign promise, Mr Trump outlined his intention to build a border wall on the US-Mexico border days after taking office
4/9 Trump and abortion
US President Donald Trump signs an executive order as Chief of Staff Reince Priebus looks on in the Oval Office of the White House. Mr Trump reinstated a ban on American financial aide being granted to non-governmental organizations that provide abortion counseling, provide abortion referrals, or advocate for abortion access outside of the United States
5/9 Trump and the Dakota Access pipeline
Opponents of the Keystone XL and Dakota Access pipelines hold a rally as they protest US President Donald Trump's executive orders advancing their construction, at Columbus Circle in New York. US President Donald Trump signed executive orders reviving the construction of two controversial oil pipelines, but said the projects would be subject to renegotiation
6/9 Trump and 'Obamacare'
Nancy Pelosi who is the minority leader of the House of Representatives speaks beside House Democrats at an event to protect the Affordable Care Act in Los Angeles, California. US President Donald Trump's effort to make good on his campaign promise to repeal and replace the healthcare law failed when Republicans failed to get enough votes. Mr Trump has promised to revisit the matter
7/9 Donald Trump and 'sanctuary cities'
US President Donald Trump signed an executive order in January threatening to pull funding for so-called "sanctuary cities" if they do not comply with federal immigration law
8/9 Trump and the travel ban
US President Donald Trump has attempted twice to restrict travel into the United States from several predominantly Muslim countries. The first attempt, in February, was met with swift opposition from protesters who flocked to airports around the country. That travel ban was later blocked by the Ninth Circuit Court of Appeals. The second ban was blocked by a federal judge a day before it was scheduled to be implemented in mid-March
SANDY HUFFAKER/AFP/Getty Images
9/9 Trump and climate change
US President Donald Trump sought to dismantle several of his predecessor's actions on climate change in March. His order instructed the Environmental Protection Agency to reevaluate the Clean Power Plan, which would cap power plant emissions
Mr Trump, who recently accused former president Barack Obama of wiretapping his New York skyscraper during the campaign, took to Twitter before the hearing began, accusing Democrats of making up allegations about his campaign associates' contact with Russia during the election.
He said Congress and the FBI should be going after media leaks, and maybe even Hillary Clinton, instead.
Mr Trump tweeted: “The real story that Congress, the FBI and others should be looking into is the leaking of Classified information. Must find leaker now!”
Mr Trump also suggested, without evidence, that Mrs Clinton's campaign was in contact with Russia and had possibly thwarted a federal investigation.
US intelligence officials have not publicly raised the possibility of contacts between the Clintons and Moscow.
Officials investigating the matter have said they believe Moscow had hacked into Democrats' computers in a bid to help Mr Trump's election bid.
Monday's hearing, one of several by congressional panels probing allegations of Russian meddling, could allow for the greatest public accounting to date of investigations that have shadowed the Trump administration in its first two months.
US intelligence agencies concluded that Russia meddled in the campaign to help Mr Trump defeat his Democratic rival Mrs Clinton. The FBI has also been investigating ties between Russia and Trump advisers and associates during the campaign.
Associated Press contributed to this reportReuse content