The National Transportation Safety Board provided an update Wednesday on the investigation into the failure of a Boeing Co. 787 engine, which occurred last month in South Carolina.

The 787 involved was powered by General Electric’s GEnx engine.

The NTSB has determined that a mid-shaft engine fan fractured during the failure. The safety board is continuing its investigation. However, the NTSB noted that the failure is a “specific engine design feature” that “generally does not pose immediate safety risks.”

During the July 28 incident, hot debris shot out of the 787’s engine and sparked a fire at the Charleston airport. The airport closed for an hour.

Japan Airlines is the only current airline operating 787s with GEnx engines. Dreamliner launch customer All Nippon Airways operates 787s with Rolls-Royce engines.

Air India, which is set to take delivery of 787s with GEnx engines, has said it would wait for the NTSB report before doing so.

Boeing builds 787s both in North Charleston and in Everett. Air India is to receive the first 787 assembled in South Carolina.

Here’s the NTSB update:

WASHINGTON – The National Transportation Safety Board continues its investigation of the July 28, 2012 contained engine failure that occurred on a Boeing 787 Dreamliner during a pre-delivery taxi test in Charleston, South Carolina. A contained engine failure is a specific engine design feature in which components might separate inside the engine but either remain within the engine’s cases or exit the engine through the tail pipe. This design feature generally does not pose immediate safety risks.

Last week, the NTSB sent an investigator to the scene to gather information on the incident and subsequently launched a full investigation into the cause of the failure, led by NTSB Investigator-in-Charge, Mr. David Helson.

On August 1, 2012, a team of experts from the NTSB, FAA, Boeing and GE Aviation specializing in engine systems and metallurgy traveled to a GE facility in Cincinnati, OH to disassemble and examine the failed GEnx engine. GE is the manufacturer of the GEnx engine. The parties to the investigation have been extremely cooperative in assisting NTSB personnel in its review and assessment.

As a result of the investigative work to date, the NTSB has determined that a fan mid-shaft on the failed GEnx engine fractured at the forward end of the shaft, rear of the threads where the retaining nut is installed. The fan mid-shaft is undergoing several detailed examinations including dimensional and metallurgical inspections.

The GEnx engine is a newly designed aircraft engine. It is a “dual shaft” engine, meaning that one shaft connects the compressor spool at one end to the high pressure turbine spool at the other end. A longer “fan shaft” connects the fan and booster in the front of the engine to the low pressure turbine in the back.

The cockpit voice recorder and flight data recorder, which is a combined unit on the 787 Dreamliner, was transported to the agency’s Recorders Laboratory in Washington, DC for processing and readout. Both recordings captured the event and analysis is ongoing.

This investigation is ongoing. The information released today is factual in nature and does not include any analysis. Additional factual information may be released as it is developed.