A 42-year-old labourer, who had taken part in the human trial of India's indigenous Covid-19 vaccine Covaxin developed by Bharat Biotech, died nine days later in Madhya Pradesh's capital city Bhopal, officials said today.

Bharat Biotech said in a statement that "preliminary reviews" indicate that the death of Deepak Marawi was unrelated to the vaccine trial.

Rajesh Kapur, vice chancellor of People's Medical College and Hospital where the trial was conducted, told the media that Deepak had participated in the Covaxin trial on December 12. He died nine days later.

Bharat Biotech claimed Marawi had fulfilled "all the inclusion and exclusion criteria to be accepted as a participant in the Phase-III trial".

He was reported to be healthy in follow-up calls seven days after his dosing and no adverse reaction was observed or reported, the Hyderabad-based company said.

"The volunteer passed away nine days after the dosing and preliminary reviews by the site indicate that the death is unrelated to the study dosing. We cannot confirm if the volunteer received the study vaccine or a placebo as the study is blinded," it added.

Madhya Pradesh Medico Legal Institute Director Ashok Sharma said the doctor who performed autopsy suspected that Marawi died of poisoning. However, the exact cause of the death would be known from his viscera test, he added.

"After Marawi's death on December 21, we informed the Drug Controller General of India and Bharat Biotech," Kapur said.

He claimed Marawi had volunteered for the trial and was examined and "all protocols were followed and Marawi's consent was taken before allowing him to participate in the trial."

Kapur said Marawi was kept under observation for 30 minutes after the trial as per guidelines before he was allowed to go. "We monitored his health for 7 to 8 days," he added.

Family members of Marawi claimed that when he returned home, he felt uneasy and experienced some health problems.

"He complained of a shoulder pain on December 17. Two days later, he frothed at mouth. He refused to see a doctor saying he would be alright in a day or two. When his condition deteriorated, he was rushed to hospital but he died on the way (on December 21)," they added.

The Drugs Controller General of India (DCGI) last week approved Oxford-AstraZeneca vaccine Covishield, manufactured by the Serum Institute of India, and Covaxin of Bharat Biotech for restricted emergency use in the country.