Civil aviation director Alejandro Argudin said the search of the area could take several days and that authorities were trying to determine if the Learjet, made in 1969, carried a black box flight data recorder.
"We are examining what modifications were made to the equipment to improve the plane and see for sure if a black box exists or not," Argudin told reporters.
Revered as the "Diva de la Banda," the soulful singer and mother of five had given a concert in the industrial city of Monterrey late Saturday before her fateful flight.
She was heading to Toluca, near Mexico City, to participate as a coach in Mexico's version of the television singing contest "The Voice."
Her California driver's license and some of her clothes were found at the crash site, where the wreckage spread over a radius of up to 300 meters (yards) in rough terrain.
In Washington, the US National Transportation Safety Board confirmed Rivera was among the seven fatalities and attributed the crash to "unknown circumstances" pending the outcome of an investigation.
In a statement, it added that it was dispatching investigators "specializing in airplane airworthiness and flight crew operations" to help Mexican authorities in their probe.
The same Learjet was involved in a landing mishap in Amarillo, Texas, in July 2005, in which none of the four people on board were injured, according to NTSB records.
Born in Long Beach, California to Mexican parents, Rivera was a star in the northern Mexican music genre known as banda, selling 15 million records and winning Billboard Latin Music awards.
She was divorcing her third husband, former baseball pitcher Esteban Loaiza.
"So sad!! Praying for Jenni Rivera's children and family and the passengers' families. God bless them!! Rest in peace," US music and film star Jennifer Lopez wrote in one of the many condolences expressed on Twitter.
"My heart breaks for the loss of Jenni Rivera and everyone on the plane," added actress Eva Longoria. "My prayers go out to her family. We lost a legend today."
Fans lit candles outside the Monterrey Arena where Rivera had performed over the weekend. One fan left a sign next to her picture with the words "Inolvidable" ("Unforgettable"), one of her song titles.
A handful of fans gathered outside the home of Rivera's mother south of Los Angeles to hear the latest news from her family.
"We lost a star," glassworker Martin Delgado, 44, told AFP. "She was a woman who battled a lot and was an example for many people, many women."
--------------------------------------------------------------------------------------------------------------------