A woman has been killed and five more people injured after an out-of-control truck laden with bricks smashed into commuters at an inner-city bus stop during a “horrific” peak-hour crash.

The truck driver told police he might have had a “medical episode” about 7.45am on Wednesday before his vehicle clipped the gutter, veered across oncoming traffic and hit a traffic light in eastern Sydney.

“We didn’t know what it was (at first),” witness Eunice Chalice said.

“It was like an explosion.”

The B-double – with the traffic light still attached to its front – then ploughed through people waiting at a bus stop near Green Square railway station in Alexandria. It hit an abandoned building before stopping in the middle of the road, NSW Police say.

One woman died at the scene. Paramedics were initially unable to reach her body under the rubble of the partially collapsed building.

“The first paramedics on scene arrived to a horrific scene,” NSW Ambulance Acting Superintendent Steve Vaughan said.

Patients were strewn over 50 metres, he said.

“They were able to identify a truck driver who was trapped in his vehicle, multiple pedestrians laying around on the footpath and two other people sitting in vehicles,” Acting Superintendent Vaughan said.

He said the male driver was trapped for 45 minutes, and was “critically unwell”.

“Part of the truck [was] compressing his legs, which required significant intervention from the medical team and collaboration with police rescue and paramedics to remove him from the vehicle,” Mr Vaughan told the ABC.

A woman in her 20s was also critically injured. She was taken to hospital and had emergency surgery later on Wednesday.

Another two people suffered serious injuries.

Supt Holland, Redfern PAC Commander speaks to media after one dead and several seriously injured in #Alexandria truck crash pic.twitter.com/7bErGeXxOt

— NSW Police Force (@nswpolice) December 11, 2018

NSW Police Superintendent Andrew Holland said the driver was also taken to hospital after being freed from the truck.

“He may have had a medical episode, but that is yet to be confirmed,”  he said. “An investigation will either rule that out or in. He’s obviously in shock.”

Superintendent Holland said the dead person was “knocked into the building by the sheer force of the truck”.

“All pedestrians were on one side of the road and they’ve all been conveyed to local hospitals, and they are very, very serious injuries for the majority of them,” he told the ABC.

Witness Robert Leash said the crash “freaked him out”.

“I didn’t know there were people there when all that happened,” he said.

“It was a whole lot worse than I thought it was.”

Police say there is nothing to indicate the incident was terror-related.

Nearby businesses remain without power and several staff from a construction zone across the road were sent home after witnessing the traumatic event.

Botany Road, a major artery connecting Sydney’s inner-city suburbs and the airport, was to remain closed for several hours on Wednesday.

Bus routes were missing several stops in the area, with some routes delayed up to 70 minutes.

Drivers had been advised to take alternate routes.

-with agencies