Boston Marathon bombing: Two suspects spotted carrying backpacks and acting suspiciously, authorities say

Investigators may have spotted two Boston Marathon bombing suspects carrying backpacks and acting suspiciously, in what could be the biggest break in the case yet.

However, no arrests had been made and no suspects had been identified by name, two US government officials said.

An earlier report by CNN that a bombing suspect had been arrested was inaccurate, the network said, and a stern rebuke from the Federal Bureau of Investigation.

But a law enforcement official told the Associated Press on Wednesday that "there is an image of a person, of a potential suspect."

Investigators were working "to locate and identify that individual," the official added.

The LA Times, meantime, reported that the authorities had pinpointed two men carrying backpacks as possible suspects.

The authorities had obtained clear images of the mens' faces and said they were acting suspiciously around the time of the bombings.

The Times cited a federal law enforcement official as saying that the surveillance camera caught an image of at least one of the men leaving a backpack near the finish line.

The development less than 48 hours after the explosions at the Boston Marathon finish line killed three people and injured 176 others.

The bombings, deemed the worst attack on US soil since Sept. 11, 2001, killed 8-year old Martin Richard, 29-year-old woman Krystle Campbell, and a Boston University graduate student and Chinese citizen, Lu Lingzi.

Separately on Wednesday, Boston's federal courthouse was evacuated after a security scare.

According to Reuters, evacuees included courthouse staff, lawyers, attorneys and two cribs with children in them from the courthouse daycare center. The building was reopened after an hour.

Boston City Council President Stephen Murphy, citing Boston police, said investigators matched an image on surveillance footage with witness descriptions of someone leaving the scene.

According to the AP, he said:

"I know it's very active and very fluid right now – that they are on the chase. They may be on the verge of arresting someone, and that's good."

The Boston Globe wrote that the images may have captured the suspect planting one of the two bombs.

Separate media reports indicated there were pictures of the suspect running away while other people slumped to the ground during the blast.

The FBI claims to have launched a "worldwide hunt" for the perpetrators.

Massachusetts Governor Deval Patrick, meantime, appealed for patience over the pace of the investigation:

He told CNN:

"They are making progress. But it's going to take time. Every hour, we're closer."