Two workers were killed and three others were injured in an accident at a construction site for a 51-story building near Tokyo Station on Tuesday.

One of the injured workers remained unconscious, according to authorities.

The workers were caught up in the incident when a steel column weighing about 15 tons collapsed, and four of the victims fell from the seventh floor to the third floor of the site in the Yaesu district of Chuo Ward, at 9:20 a.m., according to the Tokyo Metropolitan Police. The cause of the incident remains under investigation, NHK reported.