Pennsylvania crash kills 45

SOMERSET, Pennsylvania (CNN) -- A United 757 jet with 45 people aboard crashed Tuesday about 80 miles southeast of Pittsburgh and local officials said there were no survivors. The airline said a second United flight crashed but it did not know where.

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Flight 93 originated in Newark and was bound for San Francisco with 38 passengers, five flight attendants and two pilots when it crashed Tuesday morning in Somerset County, said spokeswoman Jenna Ludgate.

Friends and relatives of passengers on that flight should call 800-932-8555, she said.

"United is deeply concerned about a further flight, United Airlines #175, a Boeing 767 which was bound from Boston to Los Angeles," she said.

"United is working with all the relevant authorities, including the FBI, to obtain further information."

Meanwhile, in accordance with FAA directives, a worldwide ground stop of all of United's flights continues, she said.

Emergency officials at the scene of the Somerset crash told CNN there were no survivors. Similar reports came earlier from police and hospital officials.

The plane passed over Shanksville, and crashed south of Route 20 near a Indian Lake at 10:10 a.m., witnesses said. They said the impact shook buildings in Shanksville, 10 miles east of this western Pennsylvania city 80 miles south of Pittsburgh.