Updated at 4:40 a.m. ET Saturday
A suspect in Friday's truck attack in Stockholm has been arrested, according to a Swedish prosecutor.
Police in Sweden say the man they have arrested is "likely" the driver of a truck which drove into pedestrians on a major shopping and tourist street in Stockholm, causing multiple injuries and fatalities.
The vehicle, a stolen beer delivery truck, plowed through the pedestrian street and crashed into an upscale department store. Four people died and 15 were injured, according to police.
"It is likely him," police spokesman Lars Bystrom told The Associated Press Saturday morning.
Prosecutor Hans Ihrman said authorities identified the man as a suspect "of terrorist offenses by murder," the AP reports. Ihrman said the man should have a pre-trial hearing on whether he will remain in custody before the middle of the day Tuesday or be released.
Ihrman and Bystrom told the wire service that police have only arrested one person in their investigation of the attack.
Authorities earlier said they are investigating the incident as a possible terrorist attack. No group has yet claimed responsibility.
One child and eight adults who were injured remain in Karolinska hospital, the AP reported early Saturday, and six people have been released.
"This is a day of mourning for Sweden. The attack targeted our society at its most vulnerable — when we are going about our daily lives. Our thoughts go to those affected and to their families," Swedish Prime Minister Stefan Löfven said in a statement on the government's website.
The government says flags will be flown at half mast at government offices on Saturday, starting at 8 a.m.
On Friday, police had questioned two people they did not identify as suspects. (At one point Sweden's prime minister said someone had been arrested, but police said that was not true.)
Then authorities released a photo of a man they said was wanted in connection with the crash.
"The picture shows a man clad in a hooded jacket on an escalator in what appears to be the Stockholm metro," Radio Sweden reported. "The police stressed he is not suspected of the deed, but is wanted for questioning."
Prime Minister Löfven, speaking shortly after the incident, said there were indications the truck hit pedestrians as "a terror attack." But Radio Sweden reports that the Swedish Security Service says there is no confirmation the incident was an act of terrorism.
Police were unable to confirm early reports of gunfire at the scene.
The incident occurred on Drottninggatan, or Queen Street, a popular walking destination lined with shops. The location of the crash was a pedestrian-only section of the street, according to Radio Sweden.
"It's a very crowded part of the city," Swedish journalist Lava Delo told NPR's Morning Edition.
Video footage shows people fleeing.
The Local, an English-language news agency with reporters in Sweden, reports that a brewery says the truck was hijacked from one of its staff members:
"Swedish brewery company Spendrups, which owns the truck, said it had been hijacked earlier in the day.
" 'It's one of our distribution vehicles which runs deliveries. During a delivery to the restaurant Caliente someone jumped into the driver's cabin and drove off with the car, while the driver unloads,' communication director Mårten Lyth told the TT news agency."
According to Radio Sweden, "large parts of central Stockholm are cordoned off, all metro services are canceled [and] the parliament building (Riksdag) and the government headquarters Rosenbad are in lock-down."
"A number of busy shopping locations in Stockholm have been evacuated at the request of the police," The Local reports, and theaters, concert venues and other events have also been shut down.
The department store where the truck crashed into the building is a few blocks from the site of a 2010 bombing in Stockholm, the most recent terrorist attack in the country. In that bombing, the attacker succeeded only in killing himself.
NPR's James Doubek contributed to this report.
This is a breaking news story. As often happens in situations like these, some information reported early may turn out to be inaccurate. We'll move quickly to correct the record and we'll only point to the best information we have at the time.