ALBUQUERQUE, N.M. -- A helicopter pilot had a low concentration of fentanyl in his blood during a crash in New Mexico that killed him and four other people including Zimbabwean opposition leader Roy Bennett, according to autopsy results obtained on Friday.

Fentanyl, a powerful synthetic opioid and pain medication, was found in the autopsy report for Jamie Coleman Dodd, the lead pilot in the January crash in northeastern New Mexico.

The report didn't say whether Dodd may have been taking fentanyl for health reasons. Prior reports have not indicated that drugs were a cause of the crash.

Autopsies also were performed on co-pilot Paul Cobb and wealthy businessman Charles Burnett III - also killed in the crash on a grassy mesa top east of Raton.

FILE - In this May, 10, 2010, file photo, Roy Bennett, center left, leaves the High Court in Harare, Zimbabwe, after he was acquitted of terrorism charges. New Mexico State Police said Thursday, Jan. 18 2018, that Zimbabwean opposition leader Roy Bennett died in helicopter crash. The crash on Wednesday, Jan. 17, carrying Bennett and five others went down in a mountainous rural area of northern New Mexico. TSVANGIRAYI MUKWAZHI / AP

All three men died of blunt force trauma. Burns also were a cause of death for Burnett. Bennett's wife, Heather, also died in the crash.

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Cobb had no drugs in his system, while Burnett had alcohol, amphetamine and oxycodone present in his, medical examiners determined.

The sole survivor of the crash, Andra Cobb, of Texas, later recounted her experience, saying the aircraft hit the ground with a loud bang before rolling forward, stopping upside down and bursting into flames.

"I'm watching my family burn in a fire," Andra Cobb screamed on the 911 call. "I don't know what to do. There's a big fire. I'm covered in gasoline."

A report by the National Transportation Safety Board confirmed that the weather was clear the night of the crash, and that Dodd had thousands of hours of flying experience. The pilot was able to call 911 but later died at a hospital.

Accord to BBC News, Movement for Democratic Change (MDC) party spokesperson Obert Gutu said in a statement that Bennett was a popular grassroots politician as well as a successful commercial farmer.

"Roy was a resolute and committed fighter for democratic change in Zimbabwe," Gutu said.

Bennett, treasurer-general of the Morgan Tsvangirai's MDC opposition party, previously survived a traumatic year in jail and death threats over his work.

He and his wife had traveled to New Mexico to spend their holiday with their friend Burnett, friends and family said. The wealthy businessman was described as a fun-loving person who enjoyed entertaining, at times extravagantly.