DETROIT — At the insistence of U.S. safety regulators, Honda is adding more than a million of its most popular vehicles to a growing recall for air bags that can explode with too much force.

The company said Monday it’s expanding a previous recall of passenger air bag inflators from high-humidity states to the entire nation. That will add just over a million 2001 to 2005 Civics and 2003 to 2007 Accords to the recall.

Two weeks ago Honda said it would recall about 350,000 of the cars in high humidity areas. But the recall was expanded after the National Highway Traffic Safety Administration demanded that it be done nationally. A driver’s side recall already is being done across the nation.

The ammonium nitrate propellant in air bag inflators made by Takata Corp. can burn too quickly, blowing apart a metal canister and sending shrapnel into drivers and passengers. The problem has been blamed for at least seven deaths and more than 100 injuries worldwide.