Story highlights It was transferring a patient in critical condition to a hospital

The dead included the patient, a pilot, a flight nurse and a flight paramedic

(CNN) Four people are dead after a medical helicopter crashed in Kern County, California, officials said.

The SkyLife 4 helicopter went down Thursday night, said emergency rescue spokesman Daniel Lynch.

It was transferring a patient in critical condition from Porterville Airport to the San Joaquin Community Hospital in Bakersfield, some 50 miles to the south.

Minutes after takeoff, the Fresno County Communications Center attempted to contact the chopper as part of a routine safety check. But it was unable reach the aircraft, Lynch said.

The communications center contacted control towers in Porterville and Bakersfield and established that the helicopter had not communicated with them either.

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