The White Helmets said on May 30 that four of its volunteers were wounded the previous evening when an explosive device detonated at the scene of an earlier explosion, at which the volunteers were working to extinguish a fire.

Video posted by the group shows the moment of the explosion, in the Idlib town of Addana. A local man was also injured in the blast, the White Helmets said. Credit: White Helmets via Storyful