MEXICO CITY (AP) — A 2018 helicopter crash that killed the current and former governors of the central Mexican state of Puebla was likely caused by a malfunctioning system that was known to the company flying it, authorities said Friday.

Mexico Transportation Secretary Javier Jiménez Espriú said the final investigation report concluded the helicopter “should not have flown.”

The deaths of wife and husband political power couple Gov. Martha Erika Alonso and ex-Gov. Rafael Moreno Valle stunned Mexico and raised suspicions about the cause of the crash. Moreno Valle was a prominent figure in the opposition National Action Party who had vied unsuccessfully for the party’s presidential nomination and its internal leadership, President Andrés Manuel López Obrador's Morena party had challenged the validity of Alonso's election victory.

The Agusta 109 helicopter fell about 10 minutes after taking off from a heliport within the city of Puebla on a flight to Mexico City on Christmas Eve, 2018.

It crashed in the municipality of Santa Maria Coronango, which is about 3.5 miles (5.5 kilometers) north of the city’s main airport In all, five people died.

Jiménez said mistakes by the helicopter's operator and those responsible for its maintenance contributed to the crash. Specifically investigators found records showing there was a preexisting problem with a stability system on the helicopter. One piece was found to have two loose screws inside.

The government has suspended operations by the company flying the helicopter and the company responsible for its maintenance and turned the crash investigation report over to prosecutors.

Jiménez said witnesses described the helicopter suddenly inclining to the left and diving to the ground. Investigators found no objects that had collided with the aircraft and no pieces of the aircraft that had fallen off it prior to the crash.