Under pressure from U.S. safety regulators, Takata Corp. has agreed to declare 33.8 million airbags defective, a move that will double the number of cars and trucks included in what is now the largest auto recall in history.

The chemical that inflates the airbag can explode with too much force, blowing apart a metal inflator and sending shrapnel into the passenger compartment.

The faulty inflators are responsible for six deaths and more than 100 injuries worldwide.

The announcement was made this afternoon by the heads of the U.S. Department of Transportation and the National Highway Traffic Safety Administration, which reached an agreement with Takata after sparring with the company for the past year over the size of the recalls and the cause of the problem.

Expanded recall

Eleven automakers, including Honda Motor Co. and Toyota Motor Corp., have recalled 17 million vehicles in the U.S. and more than 36 million worldwide because of the problem.

The NHTSA has established a website where vehicle owners can search the model of their vehicle to see if it is affected.

It's unclear which manufacturers will be most affected by the expansion of the recall and it's not clear how many vehicles in Canada would be affected.

Transport Canada said it has received no complaints related to this issue from Canadians, and is not aware of any incidents having taken place in Canada.

However, it has posted details about a website where Canadians can check recalls from their vehicle's manufacturer as well as a list of toll-free numbers for manufacturers.

The Takata airbag recall dwarfs last year's highly publicized recall of 2.6 million General Motors small cars for defective ignition switches and Toyota's recalls of 10 million vehicles for problems with unintended acceleration.

NHTSA administrator Mark Rosekind said investigations by the agency and auto industry haven't determined precisely what's causing Takata's inflators to explode, but said the agency cannot wait for a cause to take action.

"We know that owners are worried about their safety and the safety of their families," he said.