Two Yarmouth residents who suffered extensive burns after one threw a flammable liquid on an outdoor fire Tuesday evening were still hospitalized Wednesday.

Police have not identified the married couple, who live on Cousins Island, but Yarmouth Fire Chief Mike Robitaille said Wednesday night that the latest report he had received from Maine Medical Center listed the woman, 75, in critical condition with burns to about 40 percent of her body.

The male victim, who is in his 80s, suffered burns to about 10 percent of his body and his condition has been upgraded to stable, according to Robitaille.

The cause of the fire remains under investigation by the State Fire Marshal’s Office and the Yarmouth Fire Department, but Robitaille said, “We’ve determined that gas was thrown on the fire.” He said the couple was trying to enjoy a recreational fire in a pit rimmed by stones outside their home when it flared up. There were no other people present.

“Although people like to enjoy the outdoors, the takeaway from this is that the use of flammable liquids on a fire is almost always going to end up in disaster,” Robitaille said.

Emergency responders received calls around 8:45 p.m. from neighbors who reported they had heard an explosion at the home. The residence is located at the end of a dead-end street overlooking Casco Bay.