Concrete chunks "as big as a basketball" and bigger fell from a building under demolition in Wan Chai yesterday, damaging cars and causing traffic congestion, but injuring no one.
A chunk measuring 50cm by 50cm was found among debris that fell onto Hennessy Road from the former Asian House office block, while a taxi driver said a 25cm by 40cm piece hit his cab.
Other debris hung from the bamboo scaffolding surrounding the building, causing eastbound lanes of Hennessy Road to be closed and the tram service to be disrupted.
A construction worker and manager were arrested and questioned but were later released on bail.
"Of course, I was frightened as such a large piece of concrete hit my cab," the taxi driver said.
Another motorist, whose car was slightly damaged by falling masonry, said he accelerated when he heard "strange sounds" at about 2pm. "Then there were loud bangs and debris landed behind my car," he said.
A female passer-by said she saw pieces of concrete "as big as basketballs" littering the road.
The road was still closed at 12.30am and a Buildings Department spokesman warned at least one lane would remain closed throughout the morning.
During rush-hour, queues stretched for more than two kilometres along Hennessy Road, Queensway and Connaught Road Central. Tram services were also disrupted.
The debris from the building broke through tough nylon sheets surrounding the building before plunging into the street. At about 7pm, a crane arrived to help remove large pieces of concrete on scaffolding - one piece reportedly weighed two tonnes.
Police are investigating the cause of the incident together with officers from the Buildings Department.