One of two tunnels carrying traffic under Baltimore's harbor was closed Tuesday and another was partially shut down in response to what an official said was a security threat. The Baltimore Harbor Tunnel was closed while the Fort McHenry Tunnel was partially closed, with one lane of traffic moving in each direction, said Lt. Col. David Franklin of the Maryland Transportation Authority Police. The closures were in response to a threat, a federal law enforcement official said. The official, who spoke on condition of anonymity because of the sensitivity of the issue, did not provide further information about the nature of the threat. But another federal law enforcement official said the threat was phoned in to authorities by a person claiming to have information from abroad. Authorities are skeptical of the claim, but are checking it out nonetheless out of an abundance of caution, the official said. That source also spoke on condition of anonymity.