LOS ANGELES (AP) — Federal officials say an air-taxi helicopter that crashed two years ago on Southern California's Santa Catalina Island probably went down because of a turbine blade fatigue fracture.

The National Transportation Safety Board this month approved the investigative finding in the May 2008 crash of an Island Express helicopter that killed three people and injured three others.

The NTSB says evidence of fatigue cracking was found during examination of fractured turbine blades from the Honeywell Aerospace engine that powered the AS350-D helicopter.

Honeywell has issued service bulletins requiring inspection of similar assemblies. But the company says it does not fully agree with the NTSB's probable-cause finding.