The U.S. Food and Drug Administration (FDA) on Wednesday classified medical equipment maker Philips' expanded recall of certain ventilators in December as Class 1, or the most serious type of recall.

The company recalled the Trilogy Evo ventilators in December due to potential health risks from a type of foam used in the devices.

There have been no reported injuries or deaths to date from the recalled products, the health regulator said.

This is the latest recall to be labeled Class 1, after Philips pulled back up to 4 million of its breathing-aid machines last year amid concerns that a type of foam used in the devices could degrade and become toxic.

Earlier this month, it raised that estimate by 1 million.

($1 = 0.8880 euros)