Exclusive Books says it is investigating the circumstances around the power outage during the launch of Jacques Pauw's book, "The President's Keepers", at Hyde Park Corner on Wednesday evening.
The bookstore's CEO Benjamin Trisk did not know whether the outage was caused by an electric fault or an "unseen hand", but said that the turnout to the launch was nevertheless "astonishing".
"Hyde Park Corner is doing an investigation. At this stage, we don't know what the progress is... It certainly is an extraordinary coincidence," Trisk said.
"We are doing our own investigations as well...We will wait and see what the outcome of the investigation is. If it is the case that there was an unseen hand, we will hand what we know about the incident to the police."
He said South Africans "across the spectrum" turned up to the book launch.
"It was a magnificent crowd. Even after there was a disruption, the behaviour of people was astonishing. South Africans across the spectrum are coming into our stores to buy the book," Trisk said.
Earlier, NB Publishers CEO Eloise Wessels said the power outage seemed like too much of a coincidence in view of the threats to Pauw and the publishing company.
The HuffPost SA is awaiting response from City Power and management at Hyde Park Corner.
This is a developing story.