The National Highway Traffic Safety Administration told Chrysler Group LLC Tuesday it must expand its recall of 371,000 vehicles announced in June for risk of exploding airbags to a broader geographic area — and must alert owners by Dec. 1.

It’s the latest demand by the auto safety agency that the unit of Fiat Chrysler Automobiles NV do more to address safety concerns. It comes just days after the agency told Chrysler to move faster to fix 1.56 million Jeep SUVs at risk for rear fires.

In a letter to Chrysler CEO Sergio Marchionne obtained by The Detroit News, NHTSA deputy chief David Friedman criticized the limited “geographic scope and the slow pace of the recall.”

When inflators rupture, metal fragments are propelled towards vehicle and can cause serious injuries or deaths.

“Chrysler’s delay in notifying consumers and taking other actions necessary to address the safety defect identified is unacceptable and exacerbates the risk to motorists’ safety,” Friedman wrote.

Chrysler agreed to recall 371,000 2003-2008 Dodge Ram pickups, 2004-2008 Dodge Durangos, 2007-2008 Chrysler Aspens, 2005-2008 Chrysler 300s, 2005-2008 Dodge Dakota pickups and 2006-2007 Mitsubishi Raider pickups. Since 2013, 10 automakers have recalled 7.8 million vehicles in the United States for Takata airbags that are linked to at least four deaths and 30 injuries in Honda cars — mostly in high humidity areas. Most other automakers have already begun repairs for the recalls announcd in June.

Chrysler spokesman Eric Mayne said the company was reviewing the letter and had no further comment.

Chrysler is limiting its recall to vehicles sold or registered in high humidity areas of Florida, Hawaii, Puerto Rico and the U.S. Virgin Islands. NHTSA said the limitation was unreasonable because Takata said on Nov. 10 that passenger airbag inflators are defective in other high humidity areas.” NHTSA said the recall should also immediately include southern Georgia, Guam, Saipan, American Samoa and areas along the coast of Alabama, Louisiana, Mississippi, and Texas.

NHTSA said under federal law Chrysler is obligated “to expand its recall to include these additional areas in its current recall.” NHTSA said Chrysler must agree to expand the recall by Dec. 1 and “must make it clear that Chrysler is conducting a safety recall, to remedy a safety defect, and may not include any statements that may confuse the public as to the nature of Chrysler’s actions.

Last week, Chrysler safety chief Scott Kunselman reiterated to a Senate panel that it planned to notify owners of vehicles with possibly defective Takata airbags by Dec. 19 — a timetable some senators called unacceptable.

Takata says it will begin shipping parts for the recalled Chrysler vehicles on Dec l. NHTSA told Chrysler it must notify owners “as soon as possible” and no later than Monday. Friedman noted an injury has been reported in a 2006 Dodge Charger airbag deployment in Florida.

NHTSA called last week for Honda, Chrysler, Ford Motor Co., Mazda Motor Co. and BMW AG to expand nationwide the recalls for driver-side air bags. There isn’t enough evidence to do the same for passenger-side bags, it said. So far none have agreed.

Last week Friedman wrote Marchionne demanding Chrysler improve its efforts to fix 1.56 million Jeep SUVs at risk of gas tank fires in a rear-end collision.

Chrysler said Friday in response it wasn’t satisified with its repair rates — 3.5 percent for Grand Cherokee SUVs and 13 percent for Liberty SUVs — and vowed to do more to boost repairs and get parts to dealers.

In October, NHTSA launched an investigation into Chrysler’s recall of nearly 1 million Dodge Ram trucks for steering issues, prompted by more than 1,000 complaints from owners seeking faster repairs.

Friedman said Chrysler isn’t behaving like other automakers.

“First, unlike some other manufacturers who have more actively participated in these recalls, Chrysler has had a field incident where a fragmenting inflator injured a customer. This demonstrates the real world potential for death and injury posed by the Takata inflators installed in the recalled Chrysler vehicles,” Friedman wrote. “Chrysler’s decision to delay notification until it has replacement parts deprives its customers of the ability to take their own informed, precautionary measures if they have a car with a potentially defective airbag.”

DShepardson@detroitnews.com