The bipartisan leaders of the House Intelligence Committee said Wednesday there is still no evidence Trump Tower was wiretapped ahead of the 2016 election, refuting the president’s explosive claims that President Barack Obama authorized surveillance of his campaign headquarters.

“To date, I’ve seen no evidence that supports the claim that President Trump made that his predecessor had wiretapped he and his associates sat Trump Tower,” the committee’s ranking Democrat, Rep. Adam Schiff said. “Thus far, we have seen no basis for that whatsoever.”

Schiff said he will ask FBI Director James Comey directly about the claims when he testifies March 20.

Trump tweeted earlier this month “Obama had my ‘wires tapped’ in Trump Tower just before the victory.” The claim, presented without evidence, was met with immediate skepticism from lawmakers questioning what the Republican meant.

A spokesman for Obama called the claim “simply false.”

“Are you going to take the tweets literally? And if you are, then clearly the president was wrong,” Chairman Devin Nunes told reporters.

The California Republican said questions remain over the “interpretation” of Trump’s tweet and whether Trump associates were targeted by intelligence agencies.

Trump administration officials have struggled to explain the claims. White House press secretary Sean Spicer said last week the tweet “speaks for itself,” later saying Trump meant the Obama administration authorized a broad range of surveillance against him during the campaign.