A preliminary report by Iranian military investigators has found no evidence of criminal activity in the helicopter crash that killed former President Ebrahim Raisi and seven others.

The report, released on Thursday, stated that the helicopter had caught fire after hitting an elevated area, and no traces of bullet holes were found on the wreckage.

The investigation, conducted by the general staff of the armed forces, also revealed that the helicopter was flying on a pre-planned route and did not deviate from its designated flight path before the crash.

Additionally, no suspicious content was observed during communications between the watch tower and the flight crew.

The final communication between the president's craft and two accompanying helicopters was recorded about a minute and a half before the crash.

The wreckage was found in Iran's mountainous northwest by Iranian drones on Monday, with challenging weather conditions hindering the work of search and rescue teams.

While the report did not lay blame, it stated that more details would follow, and the investigation is ongoing. The ageing Bell helicopter that crashed was carrying Raisi and his entourage home from a trip to Iran's border with Azerbaijan on Sunday.

Raisi was laid to rest in his hometown of Mashhad on Thursday, concluding days of funeral ceremonies attended by thousands of mourners. Foreign Minister Hossein Amirabdollahian, who was also killed in the incident, was buried on Thursday in the town of Shahr-e Ray, south of the capital.

A presidential election has been scheduled for June 28. The investigation's findings will be closely watched as the country mourns the loss of its former leader and grapples with the challenges ahead.