These images show the Bumbo baby seats with seat belts installed. The ones being recalled had no seat belts.

A South African company is recalling 4 million brightly colored baby seats meant to help young children sit up while positioned on the floor.

Bumbo South Africa said Wednesday that despite warnings, parents have been placing the molded foam seats on tables and other high surfaces, and the babies have been falling out.

The company said it is issuing a safety repair kit that includes a seat belt, and urges parents not to use the seats without it.

Scott Wolfson, a spokesman for the U.S. Consumer Product Safety Commission, said parents are urged to place the seats on a soft surface even when they are on the floor.

Since 2007, 19 children have suffered skull fractures after falling from the seats -- two of them after slipping out of seats that had been placed on the floor, the CPSC said Wednesday.