A five-year-old boy died and two men were injured when an installation caught fire at Tokyo Design Week on Sunday.
The exhibit, consisting of a timber frame covered in paper, was part of an open-air student show at the event, held each year at the Meiji Jingu Gaien gardens in the Japanese capital.
Japanese TV news channels carried footage of the structure engulfed in flames. Dezeen understands that children had been playing in and around the exhibit, which was designed and built by students at the engineering department at Nippon Institute of Technology.
A boy died in the fire and two men in their forties were also injured. One was the father of the boy and was hurt while trying to rescue him, according to reports.
Tokyo Design Week representatives released a statement about the incident on Monday, expressing their apologies and intention to co-operate with police and fire department investigations.
"We deeply apologise to those who passed away and to all the bereaved families from the bottom of our hearts," said the statement, the full text of which is below.
The Japan Times reported that the blaze was quickly extinguished but that the young boy was inside the structure when it caught fire and could not be saved.
The incident happened on Sunday evening. Organisers have said they will not open the fair on Monday, which was due to be the last day of the event.
UK design journalist Max Fraser, who is in Tokyo this week, told Dezeen he cycled past the show just before the fire.
"I happened to cycle past the venue on Sunday afternoon through the park," he said. "There were lots of people around, enjoying the sunny afternoon. I could hear loud music coming from the venue. Then a friend here sent me the news."
One report suggested that the fire started when sawdust surrounding the installation was ignited by lights, but there has been no confirmation of this.