Singer 's plane was flying at 28,000 feet when it began to plummet , official says . It could have plunged at more than 600 mph , the transportation secretary says . Determining what caused the crash in northern Mexico could take up to a year . Comment: The pilot lost control of his airplane and crashed into mountains near the town of San Luis Potosi, about 100 miles from where he lived.
Singer 's plane was flying at 28,000 feet when it began to plummet , official says . It could have plunged at more than 600 mph , the transportation secretary says . Determining what caused the crash in northern Mexico could take up to a year . Some of Rivera 's family members believe she could be alive .