WHAT HAPPENED

* A bus carrying 45 students collided with a truck and rolled onto its side in Melbourne's west about 3.40pm on Tuesday

* Students from Exford Primary School were making their way home at the time

* Police said the bus was travelling west along Exford Road at Eynesbury and about to turn right on Murphys Road when it was struck

* Multiple children were trapped inside the bus before witnesses and emergency workers pulled them from the wreckage and they were transported to hospital

WHO WAS INVOLVED

* 45 children were on board the bus when the crash happened

* 18 children were taken to hospital

* 10 children sustained injuries to the body and head

* Seven children aged five to 11 remain in hospital, including one in intensive care

* One child suffered a complete amputation and several others had partial amputations

* Other injuries include crushed limbs and head and glass shard injuries

* Three patients are receiving spinal support

* A male bus driver sustained minor injuries while a male truck driver was also injured

INVESTIGATION

* The 49-year-old truck driver was charged with four counts of dangerous driving causing serious injury on Wednesday and will appear in Melbourne Magistrates Court via video link

* Investigators are still trying to establish how the crash occurred

* Mobile phone use and speed have not been ruled out but police say the investigation is ongoing

QUOTES

* "Inattention is something that we are actively looking at as part of the investigation" - Victoria Police Superintendent Michael Cruse

* "It's just distressing knowing what our kids have been through and I can only just imagine their fear" - Exford Primary School principal Lisa Campo

* "The reason I called Lisa last night and again this morning was just to make sure that she knew and understood that 'whatever you ask for ... the answer will be yes, we're there for you'" - Premier Daniel Andrews

* "My heart goes out to them and to their families at what must be an extraordinarily difficult time" - Prime Minister Anthony Albanese

PREVIOUS CRASHES

* A truck driver was charged in January over a crash with a school bus in Bacchus Marsh that left multiple students and teachers injured last year

* A bus driver struck and killed a pedestrian in Ferntree Gully in 2018 and was subsequently charged with dangerous driving causing death

* A Ballarat bus driver was jailed after injuring six people when he crashed his coach into the notorious Montague Street bridge in South Melbourne in 2016

Lifeline 13 11 14

Kids Helpline 1800 55 1800 (for people aged 5 to 25)