A ventilator model that was linked to two deadly hospital fires in Moscow and St. Petersburg has been banned by Russian authorities after dozens were sent to the U.S. The “Aventa-M” ventilator machines, which sparked fires in two hospitals, left six coronavirus patients dead. Russia has launched an investigation into the model of ventilator, which was sent to the United States as part of a larger shipment of medical supplies last month. Those ventilators “have not been deployed to hospitals,” said FEMA spokeswoman Janet Montesi. “Out of an abundance of caution, the states are returning the ventilators to FEMA.”

According to Russia’s NTV news website, doctors said a short-circuit in the ventilator caused it “literally to explode” and set fire to the coronavirus ward in St. George Hospital, St. Petersburg, on Tuesday. Another patient died three days earlier from a similar fire at a hospital in Moscow. “The ventilators were being pushed to their limits. Our preliminary information suggests there was an overload and the equipment caught fire, which set off the fire,” a source in the St. Petersburg emergency department told the Interfax news agency.