The private plane carrying popular Mexican-American singer Jenni Rivera and six companions experienced an "abrupt descent" before crashing in northern Mexico, killing everyone aboard, officials said Monday.

The aircraft "arrived at 28,700 feet and from there an abrupt descent to 9,000 occurs, which is where it crashes," the head of the DGAC civil aviation agency, Alejandro Argudin, told Radio Formula.

He said that at present authorities do not know the cause of the accident, which occurred very early Sunday morning after the Learjet 25 took off from the northern city of Monterrey en route for Toluca, near the Mexican capital.

There was no emergency radio call before the U.S.-registered aircraft made in 1969 dropped off the radar 14 minutes after taking off, Argudin said.

On Sunday, the wreckage of the completely destroyed plane were found on a ranch in a remote mountainous part of Nuevo Leon state, the capital of which is Monterrey.

In "10 or 15 days" authorities will have an initial estimate of the cause of the crash, the DGAC director said.

Argudin said that Mexican authorities have "requested the help of the U.S. Federal Aviation Administration and the U.S. National Transportation and Safety Board so they may participate in the development of the investigation."

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

In Monterrey, where Rivera gave what turned out to be her last concert, on Monday there were collective signs of grief, among them the creation of a temporary shrine of sorts with candles and flowers. EFE