Lawmakers on a pair of U.S. House committees openly battled over the investigation into Russian interference in the 2016 elections on Thursday, as FBI official Peter Strzok denied that his personal texts with an agency lawyer demonstrated bias against President Donald Trump, making the case that the FBI never leaked information about the investigation during the Presidential campaign.

"This information had the potential to derail and quite possibly defeat Mr. Trump, but the thought of expressing that, or exposing that information never crossed my mind," Strzok told lawmakers, as he staunchly defended the Russia probe.

"This investigation is not politically motivated. It is not a witch hunt, it is not a hoax," Strzok added, clearly referring to familiar complaints by President Trump about the investigation by Special Counsel Robert Mueller.

The hearing quickly turned into a partisan food fight, as Strzok refused to answer questions about the Russia investigation, citing the advice of FBI lawyers.

"The counsel of the FBI, based on the Special Counsel's equities, have directed me not to answer any questions about the ongoing investigation," Strzok said, angering GOP lawmakers.

"You are under subpoena and are required to answer the question," said Rep. Bob Goodlatte (R-VA), the Chairman of the House Judiciary Committee, who quickly threatened to hold Strzok in Contempt of Congress.

Early on in the hearing, Strzok tangled with Rep. Trey Gowdy (R-SC), who began a GOP push to question Strzok about his many text messages that were critical of President Trump during the 2016 campaign.

"So you said, 'OMG, this is effing terrifying," Gowdy quoted a Strzok text to FBI lawyer Lisa Page.

While Strzok refused to answer Gowdy's questions in that exchange about details of the Russia investigation, he did offer up one insight when prompted by Rep. Sheila Jackson Lee (D-TX), about why the probe was of such importance during the 2016 campaign.

"The information we had which was alleging a Russian offer of assistance to a member of the Trump campaign was of extraordinary significance," Strzok said. "It was credible. It was from an extraordinarily sensitive and credible source."

"The urgency for us to understand what was going on - in advance of the election, and certainly in advance of any inauguration - I can't overstate the importance of that," Strzok said.

Strzok's answer drew an immediate rebuke from Rep. Goodlatte, who had earlier threatened Strzok with contempt proceedings.

Through the afternoon, the hearing became more and more heated, as GOP lawmakers accused Strzok of not only being biased, but of directly lying to Congress under oath.

The hearing erupted, as Rep. Louie Gohmert (R-TX) not only said Strzok was lying to Congress, but then brought up his affair with former FBI lawyer Lisa Page.

Meanwhile, Republicans announced that they would question former Page - who exchanged thousands of text messages with Strzok - in a closed-door deposition on Friday and next Monday; Page had been scheduled to appear yesterday, but refused to show up for questions.