A Graco spokesperson demonstrates how to unlatch a car ... A Graco spokesperson demonstrates how to unlatch a car seat in this picture, taken from a video (YouTube).
Graco is recalling 403,222 more car seats over a potentially deadly problem with their buckles.

The maker of child products announced Thursday it would add the seats to last month's recall of more than 3.8 million car seats because they have the same buckles, which have been difficult or impossible to unlatch in certain situations.

But that may not be the end of the recall. The federal agency that regulates vehicle safety wants Graco to recall an additional 1.8 million car seats it says are at risk of developing the same problem. So far, Graco has refused.

Already, at approximately 4.2 million car seats, the recall is the fourth-largest in history for child seats. If the disputed seats are eventually added, the recall would be the largest ever.

In a written statement, Graco attributed the difficulties to dried juices or food that can gunk up the mechanism. The company said customers are experiencing "perception" and "frustration" issues, not mechanical ones.

Parents and caregivers have disputed that finding, saying the defect is much more serious. In more than 6,100 complaints reviewed by the National Highway Traffic Safety Administration, they've said the buckles can be difficult and even impossible to unlatch. In some instances, children have been trapped in their car seats until parents either cut the straps or called 911 for further help.

In at least one case, parents allege the condition caused the death of a child. The company is a named defendant in a wrongful death lawsuit filed in California, in which the plaintiff says that a Graco car seat was extremely difficult to unlatch after a car accident, and that two-year-old Leiana Ramirez died in an ensuing car fire.

NHTSA has asked company officials to submit an explanation on why the newest batch of recalled seats weren't included in the original announcement by March 20.

Michael Polk, the CEO of Newell Rubbermaid, parent company of Graco, did not respond to a request for comment Friday. A spokesperson for the company said, in a written statement, "as we have suggested all along, these buckles have gone through substantial testing that far exceed the government requirements, and they are safe and effective in restraining children."

A statement of the company's corporate principles on its website says it encourages employees "to make an impact, to take action and responsibility."

In a written filing with NHTSA, it had expanded the recall to include more seats manufactured before 2009. The recalled seats include several models produced through 2013. Since then, the company has redesigned the latch.

Models currently under recall include: Toddler Convertible Car Seats, Cozy Cline, Comfort Sport, Classic Ride 50, My Ride 65, My Ride 70, Size4Me 70, My Size 70, Head Wise 70, Smart Seat, harnessed Booster Seats, Nautilus 3-in-1, Nautilus Elite, Nautilus Plus, Argos, Argos 70 Elite, Ready Ride and Step 2.

Among the 1.8 million car seats still disputed, Graco says they are safe for parents to use. NHTSA's Office of Defects Investigation disagrees. In a written statement, it advises parents to use "an alternative car seat for transporting children until their Graco car seat is fixed."

Graco is offering "new and improved" replacement buckles to customers at no cost. Parents and caregivers can obtain one by calling 1-800-345-4109 or by emailing consumerservices@gracobaby.com.

Pete Bigelow is an associate editor at AOL Autos. He can be reached via email at peter.bigelow@teamaol.com and followed on Twitter @PeterCBigelow.

Graco Car Seat Recall Applies To 3.8M Units Of 11 Different Models

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