Rescue authorities inspect a sinkhole on an intersection in Seoul, March 24. Yonhap

Rescue workers have stepped up efforts to find a motorcyclist who fell into a large sinkhole that suddenly appeared in Seoul and left another person injured, officials said.

The 20-meter-wide and 20-meter-deep sinkhole abruptly appeared Monday at an intersection near an elementary school in Gangdong Ward, eastern Seoul, at 6:29 p.m., swallowing the motorcycle driver and injuring another vehicle driver, who passed over the section just before its collapse.

During overnight search operations, authorities discovered a mobile phone, presumed to belong to the motorcyclist, in the sinkhole at 1:37 a.m. before finding the motorcycle about two hours later, approximately 30 meters away from where the sinkhole formed.

They have yet to find the missing person, with authorities resuming search operations with heavy equipment at 7:00 a.m.

This photo shows the sinkhole on an intersection in Seoul, March 25. Yonhap

Due to the safety concerns from the sinkhole, four schools in the area — Seoul Daemyeong Elementary School, Hanyoung Middle and High Schools, and Hanyoung Foreign Language High School — were closed Tuesday.

Hanyoung Middle and High Schools notified students and parents the previous night that water would be cut off due to the sinkhole, while gas had already been shut off, making it difficult to use bathrooms and the cafeteria. (Yonhap)