Norwegian police are investigating an explosion outside the US embassy in Oslo

OSLO — Norwegian police are investigating an explosion outside the US embassy in the Scandinavian country’s capital Oslo early Sunday, officials said.

No injuries were reported. Police received reports of a “loud bang” or explosion around 1 a.m., Oslo police said in a news release.

According to Frød Larsen, leader of the Oslo Police Joint Unit for Investigation and Intelligence, the explosion was caused by some type of incendiary device. Investigators believe the embassy was the target and are looking for the perpetrators and their motive.

Larsen said the embassy entrance was damaged, but no arrests were made.

“We are early in the investigation, but we are working on multiple hypotheses,” Larsen said in a statement. “Given the current security situation, it is natural to consider whether this was a targeted attack on the American embassy. However, we are not bound by any one hypothesis.”

Local media reported that people nearby said thick smoke filled the road after the explosion. Police are talking to witnesses.

PST, the Norwegian police security service, called in extra personnel after the incident, but the country’s terror threat level has not changed, according to communications adviser Martin Bernsen.

“This is an unacceptable incident and is being taken very seriously,” said Norway’s Minister of Justice and Public Security, Astri As-Hansen.

“Police have said they are investigating the case with significant resources and there is nothing to suggest the situation poses any risk to the public.”

The US Embassy in Oslo referred media questions to the US State Department, which did not immediately return a request for comment. Neither did the Oslo police. Other details are not available.