A roof has collapsed at Hornsby Westfield after a severe storm lashed the suburb at about 2.30pm, snapping trees in half and closing roads and train lines.
Firefighters and ambulance paramedics responded quickly to the incident.
Police say there had been electricity cuts in the shopping centre and reports of roof damage.
There were reports a cinema ceiling had collapsed and the centre was evacuated.
A NSW Fire and Rescue spokesman says firefighters were using handsaws to go through the debris to see if anyone was trapped.
Paramedics have also been sent to a library in Hornsby and a demountable building near the railway station.
The spokesman said the demountable had been blown off its foundations.
A Sky News meteorologist reported winds may have reached up to 90km/h.
Police from Kuring Gai LAC (police) have released a statement on Facebook saying:
“Warning: High wind has caused numerous large gum trees to fall. At this stage Tafe car park 4 large gums down Event Cinemas roof collapse 14 inside are now out. Various trees throughout Hornsby are down. storm hit Hornsby to Manly. Westfield Hornsby is being EVACUATED. stay away from Hornsby and surrounds. We need the area cleared for SES police electrical crews and ambos. No sticky beaks stay out of the area please. check news etc for info.”
Jim Vandore was inside Westfield Hornsby when shoppers were told to evacuate.
"I did head off in the direction the carpark and it was chaos there because people were still driving in," he told SBS.
"It took a good ten minutes for anyone to move."
"People were still coming in and people were trying to reverse out. They hadn’t stopped people driving in - it was chaos.
"Stepping outside you could see that a 'mini cyclone' or something had taken place. There were trees branches everywhere. One guy told me there was a mini cyclone but I hadn’t heard anything inside. He said people were on the ground hurt. By that time there were sirens going everywhere."
