A loud blast was heard near the US Embassy in the Norwegian capital Oslo early Sunday morning, prompting a large police response, investigators said, according to Reuters.
It is not immediately clear what caused the explosion, which occurred at around 1:00 a.m. local time, or who may have been involved, the Oslo police department said in a statement.
“The police are in a dialogue with the embassy and there are no reports of any injured persons," the statement said.
Witnesses reported seeing smoke rising from the area around the embassy compound, Norwegian daily Verdens Gang reported.
The US Embassy did not immediately respond to a request for comment outside regular business hours.