The National Highway Traffic Safety Administration says it has received 25 reports from consumers about the buckles not unlatching.
According to the reports, some parents had to force the buckle open or cut the harness to free their child. No injuries were reported.
The complaints dealt with the Graco lines My Ride and Nautilus car seats that were sold from 2009 through 2011.
Graco has responded to the investigation with the following statement:
"Graco takes great pride in the quality and safety of all our products, and always strives to provide products that meet the needs of our customers. This is why Graco is fully cooperating with the National Highway Traffic Safety Administration for the investigation of the usability of the harness buckles used in some Graco car seats."
Graco's customer service number is (800) 345-4109.
The Associated Press contributed to this report.