Persson said the police car, which had left Stockholm and was heading south, veered into the path of the truck and both vehicles burst into flames. The accident occurred near Markaryd, 100 kilometers (60 miles) northeast of Malmo, Swedenâs third largest city.
âThere is nothing else for now that indicates that it was something else but a traffic accident,â Persson told a press conference.
Swedenâs top police chief, Anders Thornberg, said an investigation would take place, but was expected âto take a relatively long time.â
Swedenâs Culture Minister Amanda Lind called called it âan extremely tragic traffic accident.â
Vilks was largely unknown outside Sweden before 2007, when he drew a sketch of Muhammad with a dogâs body. Dogs are considered unclean by conservative Muslims, and Islamic law generally opposes any depiction of the prophet, even favorable, for fear it could lead to idolatry.
Al-Qaida put a bounty on Vilksâ head. In 2010, two men tried to burn down his house in southern Sweden.
Since that time, Vilks was forced to live under police protection, âdue to the fact that he made use of his freedom of expression and his artistic freedom,â Lind said Monday.
Over the years he continued to face threats to his life.
In 2014, a woman from Pennsylvania pleaded guilty in a plot to kill him.
The following year, a free-speech seminar that Vilks attended in Copenhagen, Denmark, was attacked by a lone gunman who killed a Danish film director and wounded three police officers.
Vilks, who was widely believed to have been the intended target of that 2015 attack, was whisked away unharmed by bodyguards. The gunman later killed a Jewish security guard outside a synagogue and wounded two more officers before he was killed in a firefight with police.
Police said Monday they did not know why Viksâ car drove into the wrong lane but they were investigating whether a tire might have exploded. The car had puncture-proof tires, police said.
The accident happened on the north-south E4 highway Sunday afternoon. The unmarked police car apparently ploughed through a cable guardrail separating the north- and south-bound lanes, senior police officer Stefan Siteus said at the news conference.
âWe have found residues of tire on the E4 before the accident, and we are looking into the possibility that there could have been some kind of tire explosion,â Siteus said.
The vehicle weighed 4.5 tons, which could explain how it could drive through a cable guardrail, Siteus said. He added that the speed limit at the site was 110 kilometers per hour (68 mph). An ordinary large vehicle weighs less than 2 tons.
Two investigations were taking place. Chief Prosecutor Kajsa Sundgren said she had taken over a preliminary investigation into whether âany police officer may have committed a crime in connection with the accident.â
As to whether the accident may have been caused by someone else, that is being investigated by the police, she said.
âThere is a lot of speculation going on about what may have happened, and I am careful not to contribute to them,â Home Affairs Minister Mikael Damberg told the Swedish news agency TT. âI know that the police take this very seriously.â
Born in 1946 in Helsingborg, in southern Sweden, Vilks worked as an artist for almost four decades and rose to fame for challenging the boundaries of art through several controversial works.
His most famous pieces included âNimisâ â a sculpture of driftwood built without permission in Swedenâs Kullaberg nature reserve â as well as Prophet Muhammad drawings, including the one that showed the prophet as a dog.
Vilks initially planned to display the drawing at an exhibit at a Swedish cultural heritage center, but the drawing was removed over security concerns. It went largely unnoticed until a Swedish newspaper printed the drawing with an editorial defending freedom of expression.
Several of his works, including driftwood sculptures and Mohammad drawings, including the one showing the Muslim prophetâs head on the body of a dog, are currently on display in Warsaw, Poland. The works are being shown as part an exhibition curated by a right-wing director that aims to challenge left-wing political correctness.
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Jan M. Olsen in Copenhagen, Denmark, contributed to this report.