Two years after explosive devices were planted outside the Democratic and Republican headquarters in Washington DC, authorities have quintupled the reward to $500,000 for information that could lead to the would-be bomber’s capture and conviction.

The night before the January 6 Capitol attack, when a mob of Donald Trump supporters stormed the building in an effort to prevent Congress from certifying Joe Biden’s win, the suspect placed one pipe bomb in an alley outside the Republican National Committee headquarters around 8pm ET. They put the other bomb on a park bench near the Democratic National Committee headquarters, according to the FBI.

The pipe bombs did not detonate; the suspect has remained at large. They were pictured in surveillance footage wearing a face mask, glasses, gloves, light grey Nike Air Max Speed Turf shoes emblazoned with a yellow insignia, and a gray hooded sweatshirt.

The bombs were comprised of “threaded galvanized pipes, end caps, kitchen timers, wires, metal clips and homemade black powder”, the FBI said.

The Federal Bureau of Investigation (FBI) and Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) are offering up to $490,000 of the reward, and Washington DC’s Metropolitan police department the other $10,000, authorities said.

“For two years, a dedicated team of FBI agents, analysts and law enforcement partners have been tirelessly reviewing evidence and digital media related to this case,” said David Sundberg, assistant director in charge of the FBI’s Washington Field Office, in a press release.

As of this week, the FBI and other agencies “have conducted approximately 1,000 interviews, visited more than 1,200 residences and businesses, collected more than 39,000 video files, and assessed nearly 500 tips”, the release said.

More than 950 suspects have been arrested in relation to their alleged participation in the Capitol riots, with 284 defendants facing charges involving “resisting, or impeding officers or employees”. Ninety-nine face charges for allegedly “using a deadly or dangerous weapon or causing serious bodily injury” to a law enforcement officer, the US Department of Justice said.

Some 484 of those charged have pleaded guilty to federal charges. Forty people who proceeded to trial were found guilty, justice department officials said.

The highest-profile trial related to January 6 started in late December. The former Proud Boys national chairman Enrique Tarrio and four others involved in the far-right, often violent militia group, are facing charges of seditious conspiracy and other counts related to the attack.