OSLO, March 8, (AP): Norwegian police are investigating a potential explosion outside the US Embassy in Oslo early Sunday, officials said. No injuries were reported. Police received reports of a "loud bang” or explosion around 1 am, Oslo police said in a news release.

Local media reported minor damage to an entrance of the embassy, and people nearby said the street was blanketed in thick smoke following the blasts.

Police are seeking to talk to witnesses as they search for any perpetrators. PST, the Norwegian police security service, called in additional personnel following the incident but has not changed the country's terror threat level, according to communication adviser Martin Bernsen.

"This is an unacceptable incident that is being treated with the utmost seriousness," said Astri Aas-Hansen, Norway's minister of justice and public security. "The police have stated that they are investigating the case with significant resources, and that nothing indicates the situation poses any danger to the public.”

The US Embassy in Oslo referred media queries to the U.S. State Department, which did not immediately return a request for comment. Nor did Oslo police. Other details were not available.