Children have been able to climb into the aboveground pools by using a compression strap on the outside as a foothold, the U.S. Consumer Product Safety Commission said.

About 5 million aboveground pools are being recalled, the U.S. Consumer Product Safety Commission said on Monday, citing a design flaw that has been connected to the drowning deaths of at least nine children since 2007.

The pools, which are made by Bestway, Intex and Polygroup, have a compression strap on the outside that children can use as a foothold to climb into them without a ladder or a step, the agency said.

The strap — meant to maintain the structural integrity of the pool — wraps around the pool’s vertical support legs, creating a safety hazard, according to the commission, which advised owners to immediately contact the manufacturer of their pool model to get a repair kit.

The pools were sold at retailers in the