The FBI has arrested a suspect in its investigation into pipe bombs planted near the Republican and Democratic national party headquarters in Washington, D.C., on Jan. 5, 2021, according to a federal law enforcement official familiar with the investigation.

Brian Cole was identified as the suspect in custody, according to two senior law enforcement officials briefed on the matter. The arrest marks a breakthrough in a case that has stymied investigators for nearly five years.

An FBI official says the arrest happened Thursday morning. A news conference will take place at the Justice Department on Thursday to officially announce the arrest.

A still from FBI video footage shows the individual who placed two live pipe bombs near the Republican and Democratic National Committee headquarters in Washington on Jan. 5, 2021.Federal Bureau of Investigation

Federal investigators have said an individual placed one pipe bomb near the Democratic National Committee headquarters and another near the Republican National Committee headquarters on the eve of the Jan. 6 siege on the Capitol.

The FBI has since repeatedly asked the public for information that could lead to an arrest, including releasing in January additional video of the suspect planting one of the bombs. The bureau has said the suspect is estimated to be about 5 feet, 7 inches tall and was wearing Nike Air Max Speed Turf shoes with a gold logo.

In 2023, the FBI raised the reward for providing information that led to an arrest from $100,000 to $500,000.

Lawmakers have criticized a lack of arrest in the case.

The FBI has said the pipe bombs, which were discovered Jan. 6 about 15 hours after they were placed, were viable devices that could have seriously injured or killed bystanders. The bureau has said investigators have conducted more than 1,000 interviews and reviewed tens of thousands of video files.

The mystery of the pipe bomber`s identity helped fuel some conspiracy theories, including the notion that the government had set up supporters of President Donald Trump who stormed the Capitol. Last month, the FBI debunked another one that suggested the bombs were planted by a former Capitol Police officer.

While Trump pardoned Jan. 6 rioters, including those who attacked law enforcement officers, on his first day back in office this year, the language of the pardons did not extend to the individual who planted pipe bombs near the RNC and the DNC.

John Richter, the former Biden and Clinton staffer whom the FBI wrongfully questioned about the Jan. 6 pipe bomb case, told NBC News on Thursday that he`s received a bunch of texts from friends joking about the arrest of the actual suspect.

"My phone is blowing up haha. Omg," the D.C. John Richter said in a text message.

Richter, as NBC News reported, was questioned by FBI special agents about his whereabouts on Jan. 5, 2021. Another man named John Richter was eventually arrested for storming the Capitol. That John Richter`s friend had yelled Richter`s name on the floor of the U.S. Senate, which appears to be what led the FBI to the DC Richter`s door.

Greg Rosen - who led the now-defunct Capitol Siege Section of the U.S. Attorney`s Office for the District of Columbia - told NBC News on Thursday morning that the suspect`s arrest is a reflection on the work of the type of career FBI special agents and prosecutors who have been targeted by the Trump administration for their work on the Jan. 6 cases.

"This is a testament to the incredible work of career FBI agents and prosecutors who have been working this case for years," Rosen said. "While we don`t yet know all the facts, the American people should be proud of their work."