I've heard it said many times that loose neutrals are a common cause for electrical fires. But I don't understand why a loose neutral would cause it more than a loose hot wire. The same amount of current is present in both hot and neutral.
The statement presumes a neutral shared between hot wires, which describes your main 120/240 volt service. When a shared neutral breaks, the voltage on the two hot wires is no longer 120 and 120, unless the two currents happen to be identical.
The current on the hot wire supplying what was the greater load will now cause the broken neutral to rise away from zero volts, so the loads on the more lightly-loaded line will now receive more than 120 volts, possibly igniting devices.
In other words, there will still be 240 between the lines, but the voltages to neutral could shift to, say, 70 volts and 170 volts. The greater the load difference, the greater the resulting voltage difference.
