(AP) — The death of a 35-year-old Iowa man after a Nebraska traffic stop in November has been blamed on methamphetamine.

Dakota County Attorney Kim Watson says a grand jury has found that no crime was involved in the death of Matthew Ahlsten, of Sioux City. Watson said in a news release Wednesday that autopsy tests showed Ahlsten died as a result of methamphetamine toxicity. His death was ruled an accident.

Ahlsten was a passenger in a vehicle pulled over by the trooper on Nov. 3. Ahlsten soon suffered a seizure and became unresponsive. Officials say he died before he could be taken to a hospital.

Dakota County Sheriff Chris Kleinberg has said the vehicle driver didn’t know Ahlsten and was merely giving him a ride.