Emergency crews have worked for more than an hour to free a bus driver who became trapped after the Adelaide Metro passenger service struck a concrete rail bridge support pylon at Port Adelaide. 

The crash occurred shortly before 9am on Commercial Road, near Baynes Place.

The driver, a 37-year-old Kensington Park man was taken to hospital in a serious but stable condition, while a 28-year-old female passenger was taken too hospital with non-life threatening injuries, SA Police said.

Clinton Daniels, from the SA Ambulance Service Special Operation Team, said the driver required “extensive treatment” at the scene, including blood transfusions, before he was taken to the Royal Adelaide Hospital.

“Both have significant injuries from the impact of the bus and the crumpling of the bus onto the patient themselves,” he said.

“The driver was extensively trapped through being compressed through his lower limbs.”

A man in a green SA Ambulance officer uniform .stands before a crash scene.

Clinton Daniels says the driver was trapped by his lower limbs. (ABC News)

He praised the efforts of the Metropolitan Fire Service (MFS) firefighters and the “technically difficult job” they undertook to free the driver and passenger.

MFS commander Simon Kirkmoe said the driver and passenger had been trapped on board by their lower limbs, while about four other passengers were able to get off the bus unassisted.

He said the MFS worked for about half an hour to remove the passenger from the bus, while the driver took “over an hour” to free.

“The driver presented more of a complex removal,” Mr Kirkmoe said.

“We had to use some techniques to drag the bus backwards off the pylon to then use some hand tools and hydraulic tools to actually remove the steering column in the front off the bus off of those lower limbs to enable them to be removed.”

A firefighter in a red hard hat and hi vis jacket.

Simon Kirkmoe says removing the driver was a “complex” task. (ABC News)

He said 19 firefighters were involved in the rescue, including a specialist technical rescue team.

“There is a lot of damage to the front of the bus and it would be one of the more significant accidents we’ve been to with busses in recent times,” Mr Kirkmoe said.

He said a structural engineer would assess the rail bridge before train services could resume.

“We are just ensuring that the structural integrity of the bridge, which shouldn’t be a problem, but we are just ensuring that an engineer looks at that prior to letting trains back on the line,” Mr Kirkmoe said.

Four police officers standing at the side of a crashed bus, with one on the phone.

The crash occurred shortly before 9am today. (ABC News: Isabella Carbone)

SA Police said investigations into the crash were continuing, while road closures around the scene would remain in place until the scene was cleared.