WASHINGTON — Federal investigators have increased the reward for information leading to the arrest of the person who left two pipe bombs near the Capitol the day before the Jan. 6, 2021, riot by five times, to $500,000, the FBI said Wednesday.

The announcement, made ahead of the second anniversary of the attack on the U.S. Capitol, indicates that federal investigators are still stumped when it comes to the identity of the person who left the devices outside the Republican National Committee and Democratic National Committee headquarters on Capitol Hill.

In a news release, the bureau noted that "many of the components used to build the pipe bombs were widely available for purchase in-store and online," including "1x8-inch threaded galvanized pipes, end caps, kitchen timers, wires, metal clips, and homemade black powder."

"In raising the reward for information about the pipe bomb suspect from $100,000 to as much as $500,000, the FBI and our partners are seeking to encourage the American public to take a fresh look at our Seeking Information website, which includes images and video of the suspect, the suspect’s backpack, the suspect’s shoes, the explosive devices, and a map of the route the suspect walked the night the pipe bombs were placed," the bureau said.

David Sundberg, the assistant director in charge of the FBI's Washington field office, said "a dedicated team of FBI agents, analysts, and law enforcement partners have been tirelessly reviewing evidence and digital media related to this case" for nearly two years.

The FBI, working alongside the Bureau of Alcohol, Tobacco, Firearms and Explosives and Washington police, has "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 bureau said.

Sundberg added: “We remain grateful to the American people, who have provided invaluable tips that have helped us advance the investigation. With the significantly increased reward, we urge those who may have previously hesitated to contact us — or who may not have realized they had important information — to review the information on our website and come forward with anything relevant. Despite the unprecedented volume of data review involved in this case, the FBI and our partners continue to work relentlessly to bring the perpetrator of these dangerous attempted attacks to justice.”

The FBI has arrested about 900 people in connection with the Jan. 6 attack. Last year, a former U.S. Capitol Police officer who responded to one of the bombs on Jan. 6 was convicted on a count of felony obstruction for deleting messages he sent advising a Capitol rioter to take down Facebook posts that indicated he had entered the building.

"Although these bombs did not detonate, it is important to remember the suspect walked along residential and commercial areas in Capitol Hill just blocks from the U.S. Capitol with viable pipe bombs that could have seriously injured or killed innocent bystanders," the FBI's news release said. "Moreover, the suspect may still pose a danger to the public or themselves."

Ryan J. Reilly is a justice reporter for NBC News.