After a warning is cancelled, an All-Clear condition is issued by local authorities (not the TWC) to the public when it is safe for them to return to the evacuated zones. As local conditions can cause wide variations in tsunami wave action, the All-Clear will depend on the degree of damage and can vary from locality to locality. In general, after receipt of a Tsunami Warning Cancellation, agencies can assume All-Clear status when their area is free from damaging waves for at least two hours, unless additional ETAs have been announced by the TWC (for example for a significant aftershock) or local conditions cause continued seiching or particularly strong currents in channels and harbours that require the continuation of the Tsunami Warning status. Local damage to structures and critical infrastructure, and/or secondary impacts caused by fires or hazardous materials leakage, may delay substantially the All-Clear announcement.