Afghanistan, July 7 -- The death of a former Afghan commando in U.S. immigration custody has been ruled an accident, according to an official death certificate that attributed his death to a severe allergic reaction and an acute asthma attack, while his family and supporters continue to question the circumstances surrounding the case.

Mohammad Nazir Paktiawal, 41, who served alongside U.S. Special Forces in Afghanistan, died on March 14, a day after officers from U.S. Immigration and Customs Enforcement (ICE) arrested him at his Texas home during deportation proceedings.

According to the death certificate, reviewed by The Associated Press, the primary cause of death was anaphylactic shock with acute exacerbation of asthma. The medical exa...