(VOVworld) - Investigators have found no indications of unusual behavior among the pilots and cabin crew of Malaysia Airlines Flight 370 before it took off and vanished a year ago. There were no behavioral signs of social isolation, change in habits or interest, self-neglect, or drug or alcohol abuse by the captain, first officer or cabin crew, said an interim report released Sunday from the investigation into the passenger jet's mysterious disappearance. Investigators looked into the background of each crew member. They also examined closed-circuit TV footage of the flight crew at airports and saw no signs of any change in behavior prior to the plane’s suddenly diversion and disappearance on March 8 last year. The report, citing maintenance records, said there was no evidence to suggest one black box’s battery was replaced before its expiry in December 2012. The battery on the plane's other black box, the cockpit voice recorder, was replaced as scheduled and remained within its expiry date, the report said.