Workers are returning to a Boston federal courthouse that had been evacuated because of a bomb threat amid reports of a breakthrough in the marathon bombings investigation.
The U.S. Marshals Service in Washington says the courthouse was evacuated due to a bomb threat. Spokeswoman Nikki Credic-Barrett says authorities conducted a security sweep.
Court workers are now going back inside the building, about an hour after the evacuation.
Crowds of reporters are gathered outside. The FBI and the U.S. attorney's office in Boston say no arrests have been made in the marathon bombing.