Cellphone companies are now reporting cell phone service is up, but that coverage is spotty due to to high traffic.
"A law enforcement official says cellphone service has been shut down in the Boston area to prevent any potential remote detonations of explosives.Authorities have not identified what caused the explosives that erupted at the finish line of the Boston Marathon. The official was speaking on condition of anonymity because the investigation was ongoing."
Google has also created a website to locate runners.
The police are asking that people please not assemble in large crowds.