Mexican and U.S. aviation experts are investigating the cause of the plane crash that killed Mexican-American singer Jenni Rivera and six other people over the weekend, officials said.

The remains of the singer and the other victims arrived at the coroner's office at Hospital Universitario in Monterrey, the capital of the northern state of Nuevo Leon, on Monday night.

DNA tests will be conducted before the remains are turned over to the victims' next of kin, a Nuevo Leon Attorney General's Office spokesman said.

"The results could be ready in 24 hours or they could take days, depending on the chemical quality of the remains," the AG's office spokesman said.

Officials do not "want there to be any doubts about what may have happened," Communications and Transportation Secretary Gerardo Ruiz Esparza told Mexican radio stations.

Emergency workers and crash investigators resumed the search for evidence at the crash site on Monday, a day after Rivera was killed.

The singer's Learjet 25 crashed shortly after taking off from the northern city of Monterrey en route to Toluca, a city near the Mexican capital.

The jet was not built with a black box, but one may have been installed later, aviation officials said. EFE