WASHINGTON (AP) — Two pipe bombs left at the offices of the Republican and Democratic national committees, discovered just before thousands of pro-Trump rioters stormed the U.S. Capitol, were actually placed the night before, federal officials said Friday.

The FBI said the investigation had revealed new information, including that the explosive devices were placed outside the two buildings between 7:30 p.m. and 8:30 p.m. on Jan. 5, the night before the riot. The devices were not located by law enforcement until the next day.

It is not clear whether that means the pipe bombs were unrelated to the next day’s riot or were part of the riot planning. Both buildings are within a few blocks of the Capitol.

The incident has been particularly concerning for law enforcement as officials step up security preparations ahead of the Senate’s impeachment trial of former President Donald Trump. For weeks, investigators have been worried about the potential for attacks on soft targets in the nation’s capital.

U.S. Capitol Police and agents from the FBI and Bureau of Alcohol, Tobacco, Firearms and Explosives were called to the Republican National Committee’s office around 12:45 p.m. on Jan. 6. About 30 minutes later, as the agents and bomb technicians were still investigating at the RNC, another call came in for a second, similar explosive device found at the Democratic National Committee headquarters nearby.

The two explosive devices were very similar, and both were about a foot long with end caps and wiring that appeared to be attached to a timer, two law enforcement officials familiar with the matter have told The Associated Press. Investigators are still examining the devices and their components to determine the specific compounds inside the pipe bombs, but they both appeared to contain an unknown powder and some metal, the officials said.

The officials could not discuss an ongoing investigation publicly and spoke to the AP on condition of anonymity.

The FBI released additional photos of the explosive devices on Friday, including a photograph that showed one of the devices placed underneath a bush. Officials have also increased the reward in the case to $100,000.

Steven D’Antuono, the assistant director in charge of the FBI’s office in Washington, said earlier this week that locating the person who planted the pipe bombs was a top priority for federal agents, though officials have only released grainy surveillance camera images of a potential suspect.

On Friday, the FBI said the person wore a gray hooded sweatshirt, a face mask and Nike Air Max Speed Turf sneakers in yellow, black and gray, and had been carrying a backpack.