WATCH: FBI director says agency cannot 'disclose or confirm the cause of death' of Officer Sicknick

FBI Director Christopher Wray said in a Senate hearing on Tuesday that the FBI could not "disclose or confirm the cause of death" of Officer Brian Sicknick.

Upon being asked about the cause of death by Senator Chuck Grassley (R-IA), Director Wray said "at the moment, the investigation is still ongoing."

"We can't yet disclose a cause of death at this stage," Wray continued. When asked if they have determined what the cause of death is, Wray responded that he "didn't say that."

Controversy surrounding Officer Sicknick's death came shortly after the storming of the Capitol by pro-Trump rioters on Jan 6. The New York Times initially reported based on anonymous sources that Sicknick died after being bludgeoned to death by the rioters, but weeks later admitted that there is no evidence to support this version of events.

In fact, Sicknick had returned to work after the riot feeling well, according to his family members, and it was not until later that he began to feel unwell before he died.

His cause of death is still unclear, although it is suspected by some that he may have suffered a stroke or a heart attack. Sicknick's mother reported that it was not the attack that killed him.