Swedish police are investigating whether criminal activity was behind an explosion at an apartment block that seriously injured four people.
Around 100 residents were evacuated and 16 taken to hospital after the blast caused a fire that tore through the building in Gothenburg city in Sweden.
Police have said they suspect the early morning blast was started deliberately.
"It's obvious that a crime cannot be excluded," Interior Minister Mikael Damberg told a news conference.
Unconfirmed reports in Swedish media say one of the residents of the apartment block is a police officer who had recently testified in a major gang trial.
Prime Minister Stefan Lofven, speaking alongside Mr Damberg, said he did not want to "speculate" about the blast, but added: "Everyone should know that society is always stronger than crime."
Sweden has seen a surge in gang-related crime in recent years, with firearms and explosives used to settle scores.
One resident of the block in Sweden's second city said she heard a commotion from the street at just after 05:00 (03:00 GMT) on Tuesday.
"I went out on the balcony and I was shocked. There was smoke everywhere, from every stairwell," Anja Almen, who was among the evacuated, told Reuters.
"Fire trucks with ladders were pulling people from apartments."
Residents had to be evacuated from windows and balconies as a fire afterwards spread through the building.
Police spokesman Thomas Fuxborg told a news conference that they believed a device had "probably" been placed at the site of the blast.
"We believe something has exploded that is not of natural causes," he said.
In 2020, police recorded 107 detonations nationwide and a further 102 attempted or prepared detonations, the AFP reports.
The Swedish National Council for Crime Prevention last year said the country - with a population of 10 million - had gone from having one of the lowest levels of fatal shootings in Europe to having one of the highest.
