Organics such as fuel oil, which the ship likely has on board and might also refuel. If it accidentally or "accidentally" leaks into the AN, you get ANFO, "a wi

Organics such as fuel oil, which the ship likely has on board and might also refuel. If it accidentally or "accidentally" leaks into the AN, you get ANFO, "a widely used bulk industrial high explosive". If Russia wants to nuke an European port city without using an actual nuke and while being able to at least leave some doubt whether it may have just been an accident, this certainly looks like a plausible way.