A person is dead and two more are fighting for their lives after a truck crashed into pedestrians on Botany Road in Alexandria this morning.

A NSW ambulance spokesman confirmed one person was killed in the collision just before 8am. Paramedics freed the trapped driver from the wrecked truck and his condition is listed as critical.

Two more pedestrians were critically injured and another two are being treated for injuries.

Twelve crews were called to this job and a chopper," the spokesman said.

"A truck has lost control and taken powerlines down.

"The truck has hit pedestrians and we have a total of six patients and one of those is deceased and one wastrapped in the truck".

"We're unable to comment on the cause, but there are a number of casualties and our crew is working in difficult conditions with fallen power lines".

The crash has caused traffic chaos in Alexandria as paramedics and emergency crews close the street to treat the victims.

It is understood the driver lost control of the truck and hit the pedestrians before taking down power lines.

One business owner on Botany Road said that their power went out at 8am.

"We got an alert form our Security company saying our power had been cut out and no one has said how long it will be down for," she said.

"I saw a guy in the truck in a orange high-vis and it looked like he was trapped."

Witnesses reported seeing the driver veering across three lanes before hitting pedestrians waiting at the bus stop and into an abandoned building.

NSW Superintendent Andrew Holland said one pedestrian has died five others are seriously injured.

"The driver and pedestrians were treated at the scene but unfortunately one pedestrian has died and the other victims were treated on the scene before being taken to a local hospital."

Eurice Chalice who witnessed the incident said initially he thought a crane had collapsed.

"We heard people screaming and ran over to help," Mr Chalice said.

"You hear about these things but when you see it, it's a bit of a shock."

Botany Road is closed in both directions between Bourke Street and Epsom Road, with motorists urged to avoid the area.