The government's auto safety agency says it is upgrading an investigation of collapsing rear doors on Ford Aerostar minivans, which consumers have blamed for 27 injuries.

The National Highway Traffic Safety Administration has received 85 complaints about the problem, spokesman Tim Hurd said Thursday. Some people have said they were struck in the head, back or arms as they loaded or unloaded the vehicles.A Ford Motor Co. spokesman said the company was investigating the matter on its own and cooperating with the government inquiry.