The FBI is offering a reward of up to $50,000 for information on who placed pipe bombs in the committee headquarters of US political parties in Washington.
Law enforcement agencies had received reports of two suspected devices, one each at the headquarters of the Republican National Committee and the Democratic National Committee on Wednesday, the FBI said in a statement.
The statement was accompanied by an image of a masked suspect wearing gloves and a hoodie, carrying an object.
"The FBI is offering a reward of up to $50,000 for information leading to the location, arrest and conviction," it said.
ABC News reported that bomb technicians used water cannon to blast the devices to break them apart and render them harmless on Wednesday just as supporters of US President Donald Trump stormed into the Capitol building, where lawmakers were certifying the victory of President-elect Joe Biden.
Trump initially praised his supporters but later condemned the violence.
Senators and Congressmen were forced to evacuate after the Trump supporters smashed windows and engaged in looting. The violence, which killed five people, followed a rally at which Trump exhorted supporters to fight to overturn the result of the Nov. 3 election.