The vast hole opened up at an intersection in the southeast of the South Korean capital during the evening rush hour around 6.30pm yesterday.

Dashcam footage shared with AFP by a local lawmaker shows the hole appearing abruptly in the middle of a busy street, with a motorbike being swallowed up instantly as a car narrowly escapes the same fate, sliding into the hole before somehow bouncing out.

The fire department conducted a major search, with rescue workers wearing wetsuits and “digging with their hands” alongside a rescue dog, in a frantic 17-hour hunt for the motorcyclist.

However, today “the missing person who is in his thirties, was discovered in cardiac arrest, approximately 50m from the centreline of the sinkhole”, Kim Chang-seop, an official from the Gangdong fire station, told reporters.

“He was buried at a depth of approximately 90cm and was found intact, still wearing his helmet and motorcycle boots,” said Kim, adding they “regret that we are unable to deliver better news”.

The driver of the car suffered minor injuries.

The hole is now around 20m wide and 20m deep, the fire department said.

A handful of schools nearby closed today citing safety concerns.

The cause of the sinkhole will be investigated, but the accident occurred at a site where extension work for a metro line was underway.

A Seoul city spokesman told AFP it was clear the construction could have been one of “several possible contributing factors”.

“There were several factors at play. Once the surrounding soil and debris are cleared, we will conduct a full investigation into the cause of the accident with a team of experts,” the spokesman said.

Sinkhole accidents are rare in South Korea, with fewer than 200 reported cases every year on average – significantly less than the number recorded in neighbouring Japan.