Which signals may be used to warn of a stopped vehicle that contains explosives?

You might break down and have to use stopped vehicle signals. Use reflective triangles or red electric lights. Never use burning signals, such as flares or fuses, around a: Tank used for Class 3 (Flammable Liquids) or Division 2.1 (Flammable Gas) whether loaded or empty. Vehicle loaded with Division 1.1, 1.2, or 1.3 Explosives.
[Commercial Driver's License Manual]