It was difficult to impossible to use mobile phones to check on loved ones in the wake of two explosions that rocked the Boston Marathon Monday afternoon. Cell service was congested and unreliable, and cellular providers suggested that callers use text messaging instead to reach people in Boston.
Two online registries have sprung up to try to help.
Google launched a People Finder application where users could list that they are looking for someone or that they have information about someone.
The Red Cross maintains a "Safe and Well" listing for any disaster, natural or man-made.
The Massachusetts Emergency Management Agency also said people trying to locate friends and family can reach the Boston mayor's hotline at 617-635-4500.
Their crime tips hotline is 1-800-494-TIPS.
Stay with NBC Washington and News4 for more on this developing story.