Authorities in London say they are making “significant progress” in identifying the three people they say attacked pedestrians on the London Bridge and then stabbed people out for the night in the nearby Borough Market neighborhood.

A total of seven people died in the attacks, including citizens of France and Canada, and 48 people were taken to the hospital. About three dozen of them – 21 of them critically injured – remain there, according to the Metropolitan Police.

“Work is ongoing to understand more about them, their connections and whether they were assisted or supported by anyone else,” said Assistant Commissioner Mark Rowley in an updated statement Sunday. “As I think you are aware there are searches ongoing in east London, and 12 arrests have been made. There is of course more to do, and we will work relentlessly to establish the facts.”

Police say a white Renault van rented by the attackers mounted the pavement just before 10 p.m. and began mowing down London Bridge pedestrians before it was abandoned. The three attackers left the van and continued brutal knife attacks in the pubs and streets of the busy Saturday-night neighborhood.

All three attackers wearing what turned out to be fake suicide vests where shot dead by police, who ended the incident eight minutes after it began.

British authorities have not identified any of the victims or the attackers, and said there may be delays because some of the victims’ loved ones are abroad.

Image: Metropolitan Police UK