Two people have died in a deadly plane crash at a small airport in Arizona, authorities said Wednesday.The plane ran off the runway and burst into flames, Marana Mayor John Post said.City spokesman Vic Hathaway said there were two people on board the plane. He has not been identified. No other injuries were reported, and no other aircraft were involved, the Marana Police Department said in a news release.Police said the National Transportation Safety Board is investigating the cause of the accident.Marana is about 32 km northwest of Tucson.