That looks to me like the battery compartment
Tending to think the same, if engine shrapnel had punctured the the engine deck could have allowed oil/fuel from busted lines to drain into the compartment, no engine fire indications perhaps in that case. We had a Turbomeca in a 76 disintegrate and cause oil lines to burst, caused a fire, authorities considered the design of oil lines not an airworthy installation, didn't see that idea get up though.