17/07/2016 7:47 PM AEST | Updated 18/07/2016 1:39 AM AEST

Nice Attacks: Two More Arrests As Police Piece Together How The Attack Unfolded

'Bring more weapons': The messages of a killer moments before his attack.

Pascal Rossignol / Reuters
The growing tributes to the victims of the Bastille Day attack, France's third terror attack in 18 months.

Two more people have been arrested over the Nice terror attack that left 84 people dead on Thursday.

A man and a woman with alleged links to the killer were arrested on Sunday morning (CEST), bringing the total to five people still being held in custody. Truck driver Mohamed Lahouaiej-Bouhlel's estranged wife had been held since Friday but was released Sunday without charges.

The arrests follow raids across Nice, as information is beginning to emerge that the attacker was not operating alone.

According to a representative for Paris' prosecutor's office, in the moments before the attack, Bouhlel sent a text message to an unnamed person saying "Bring more weapons".

An earlier message reportedly read "It's good. I have the equipment."

The last message was sent at 10:27pm, about half an hour before Bouhlel drove his rented truck down the bustling Promenade des Anglais, leaving carnage in his wake. At least one of his messages was sent to one of the people currently in police custody.

Eighty-five people are still in hospital being treated for their injuries, 18 of whom -- including one child -- remain in a life-threatening condition, the French health minister said.

Mohamed Lahouaiej-Bouhlel reportedly scoped out the Nice promenade with his rented 19 tonne refrigerated truck in the two days leading up to Bastille Day, when he ran down victims, killing 84 - including ten children - who had gathered on the promenade to watch the Bastille Day fireworks.

Although ISIS claimed responsibility for the attack on Saturday, authorities have yet to find any direct links between the truck driver and the terrorist group.

"The person who carried out the operation in Nice, France, to run down people was one of the soldiers of Islamic State," the ISIS-supporting news agency Amaq wrote on a statement on its Telegram account.

"He carried out the operation in response to calls to target nationals of states that are part of the coalition fighting Islamic State," the statement said.

French Prime Minister, Manuel Valls, said in an interview with newspaper Le Journal du Dimanche that "we know now that the killer was radicalized very quickly," although he didn't provide details of how this radicalisation took place.

Although he had a police record and was known to police as a petty criminal, the 31-year-old Tunisian was not on the radar of intelligence services and had reportedly only started attending a mosque earlier this year.

Neighbours and associates have created a picture of him as a mentally unstable "loner" who appeared aggressive, but -- at least until the past few months -- displayed little inclination towards radical Islam.

His father, Mohamed Mondher Lahouaiej-Bouhlel, told Agence France-Presse that his son had battled with depression.

"He didn't pray, he didn't fast, he drank alcohol and even used drugs," he said.

According to French media, a psychiatrist who saw him in 2004 said Bouhlel had come to him because of behavioural problems and that he diagnosed him as suffering from "the beginnings of psychosis."

Bouhlel drove for two kilometres down the seafront boulevard, swerving from side to side to maximise the number of casualities, before finally being shot dead by police.

The memorial at the Promenade des Anglais continues to grow as locals and tourists place flowers, French flags, teddies and candles at the site of the attack.