Organisers of the Christchurch marathon say they have had assurances the implosion of the city's former police station will not affect the race.
The marathon course, which is returning to the central city for the first time since 2011, runs directly past the building.
The implosion was scheduled to take place on 30 May, but if the weather is bad, the plan was to carry it out the next day - the same day as the marathon.
Race organiser Chris Cox said he only found out about the plans yesterday.
But he said the contractors have promised not to implode the building on marathon day and to ensure the course is clear of any debris if it happens as scheduled the day before.
"At the end of the day you could potentially have a heath and safety issue and it's my responsibility to ensure from a health and safety perspective the event is safe.... there's going to be 5000 runners past that construction site."