RALEIGH, N.C. -- Officials now know the cause of a State Highway Patrol helicopter crash in Raleigh last month.

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• A preliminary report from the National Transportation Safety Board shows a transporter clamp was hooked during the June 19 take off at the Garner Road heliport
• Officials say this caused the chopper to roll uncontrollably until the main rotor blades struck the ground

A preliminary report from the National Transportation Safety Board shows a transporter clamp was hooked during the June 19 take off at the Garner Road heliport.

Officials say this caused the chopper to roll uncontrollably until the main rotor blades struck the ground.

The NTSB obtained that new information from the pilot's written statement.

The pilot and his passenger were not seriously hurt.

The report says the crew was preparing to take photos near Raleigh-Durham International Airport when the crash happened.