Monterrey , Mexico ( CNN ) -- Even as Mexico 's top transportation official said the plane carrying Jenni Rivera spiraled to the ground in a tailspin that may have surpassed 600 mph , some of the singer 's family members were holding out hope on Wednesday . The plane was flying at 28,000 feet when it began to plummet , Gerardo Ruiz , Mexico 's transportation secretary , told reporters . It crashed in a mountainous area 9,000 feet above sea level , he said . Determining what caused Sunday 's crash could take up to a year , officials said . Authorities were still working Wednesday to identify remains found at the crash site in a remote area of northern Mexico . Rivera and six others were thought to be on board the plane , which lost contact with air traffic controllers soon after takeoff . In California , the Mexican-American singer 's mother said her grandchildren still think Rivera is alive . `` They continue thinking that their mother is OK , that God could perform a miracle , '' said Rosa Saavedra , noting she was trying to stay strong to support them . Pedro Rivera Jr. , one of the singer 's brothers , said the family was waiting to read a document detailing her wishes that she had left with a sister about a month ago . `` She can not read it yet , she ca n't say anything to us yet , until we are 100 % sure that Jenni is no longer with us , '' he said . Known to fans as `` La Diva de la Banda '' or The Diva of Banda Music , Rivera was well-established as a musical powerhouse with her Spanish-language performances of regional Mexican corridos , or ballads . For fans , the nickname captured her powerful voice and the personal strength many admired . In recent years , she had been working to crack the English-language U.S. market and was reportedly on the verge of a crossover with a sitcom inspired by the success of `` I Love Jenni , '' a Spanish-language reality TV show on Telemundo 's mun2 network . Rivera sold 15 million records , according to Billboard , and recently won two Billboard Music Awards , including favorite Mexican music female artist . In October , People en EspaÃ±ol added her to its list of the 25 most powerful women . She performed at a concert in Monterrey on Saturday night before boarding the Learjet , which took off early Sunday and lost contact with air traffic controllers about 60 miles into the trip . Plane 's owners tied to troubled businessman . Just hours before she died , Rivera opened up to reporters about her divorce and the inner strength she found , thanks to her family . `` I 'm so happy . So many strong things have happened in my life , '' she said . `` I ca n't get up in the negative , which destroys you . '' CNN en EspaÃ±ol 's Krupskaia Alis and Jaqueline Hurtado contributed to this report .
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 .