The driver of a 32-tonne tipper truck which struck and killed four people has been arrested on suspicion of causing death by dangerous driving and manslaughter by gross negligence.
Philip Potter, 19, from Brinkworth in Wiltshire, was transporting sand and gravel in Lansdown Lane in Upper Weston, Bath, Somerset, just after 4pm on February 9.
The Scania truck first hit and killed Mitzi Rosanna Steady, four, from Bath, and her grandmother, who remains in a critical condition in Southmead Hospital in Bristol.
It went on to collide with a number of other vehicles on the road before overturning on to a Volvo at the bottom of the hill - killing the three men inside.
They were Robert Parker, 59, from Cwmbran, and electricity company director Philip Allen, 52, and taxi driver Stephen Vaughan, 34, both from Swansea.
Avon and Somerset Police arrested Mr Potter and a 28-year-old man, believed to be his boss, this morning.
A force spokesman said: "We have this morning arrested two men following the death of four people in Bath last week.
"It follows the incident in Lansdown Lane on Monday evening (February 9) when a tipper truck carrying aggregate was in collision with a number of vehicles and two pedestrians," the spokesman said.
"A 19-year-old man has been arrested on suspicion of causing death by dangerous driving and manslaughter by gross negligence.
"A 28-year-old man has been arrested on suspicion of causing manslaughter by gross negligence.
"Their arrests follow the deaths of four-year-old Mitzi Steady, from Bath, Robert Parker, aged 59, from Cwmbran, Phillip Allan, aged 52, from Swansea, and Stephen Vaughan, aged 34, from Swansea.
"The girl's grandmother who was also injured in the incident remains in a critical condition in Southmead Hospital."
Mitzi's family previously released a photograph of the little girl and a short statement saying: "Mitzi Rosanna Steady, aged four, loved and missed by us all."
Staff at Snapdragons Nursery in Weston, which Mitzi attended, said their "hearts go out" to the little girl's family.
"We will always miss her smile and her warmth," they said.
Mother-of-two Katie D'Arcy, who lives locally, said she would often see Mitzi walking along the road with her grandmother.
"She was a gorgeous little girl - it's just unbelievable and it's just so shocking when it is somebody you know," she said.
Tributes were also paid to Mr Vaughan, from Penyrheol, near Gorseinon, Swansea, who ran luxury taxi firm EliteXecutive Travel and married fiancee Sian in Turkey last year.
In a statement released by Avon and Somerset Police, Mrs Vaughan said: "Steve was infectious - when he smiled, the whole room would smile.
"Myself, Steve's parents and family are very proud of the man he was, a true gentleman and we were so privileged to have been a part of his life.
"We are devastated that he was taken away from us so soon.
"We had only been married six months and I was honoured that he chose me to be his wife. Steve was dedicated to his family and his business which made him a well-respected businessman.
"Even though we are going through our loss, our hearts go out to all the other families that have lost loved ones and we would like to thank the emergency services and the local community for everything that they have done for us at this sad time."
Father-of-two Mr Allen, who lived in Loughor, Swansea, with wife Caroline, was a resources and external affairs director for Cardiff-based Western Power Distribution.
Relatives comforting Mrs Allen, 53, said she was too distressed to speak to the media following his death.
Around 400 residents attended an hour-long prayer service for the victims at All Saints Church Weston, led by Rector Patrick Whitworth, last Tuesday.
Children, parents and grandparents lit candles and used colourful pens to write messages of condolence on white fabric.
Bereavement counselling is being offered to children at Weston All Saints Primary School, some of whom witnessed the collision.
Books of condolences have been opened in libraries at Bath and Weston, while tribute flowers have been left at a nearby church.
A fundraising page set up by Mitzi's family in memory of the little girl has raised almost £7,000 for charity - smashing its £1,000 target.
The JustGiving page, created by her father Andrew on Sunday evening, said Mitzi died on the road next to "her brother and sister's school".
It initially aimed to raise £1,000 for road safety charity Brake but hundreds of people have since donated.
A statement on the page yesterday said: " What an amazing response, we are very touched. Some of the messages written have been really lovely and reminded us to think of the other victims.
"When fundraising is complete we'll ask Brake if there is anything specific they can do for the Weston community and/or Lansdown Lane."