The blast was heard from the embassy compound in ​western Oslo at around 1am, and ​smoke was seen rising from the area, eyewitnesses ⁠said.

“There was a very thick layer of smoke ​on the street,” said Sebastian Toerstad, 18, a high ​school student who drove past the embassy at the time of the incident.

“There was some damage to the entrance,” Toerstad told ​Reuters.

Oslo police said the blast had occurred at ​the entry to the consular section.

Two police technicians wearing white overalls ‌were ⁠later seen working at the site.

No further explosive devices had been found in the area, police said.

“Investigations have been carried out at the scene with the ​aid of ​dogs, drones ⁠and a helicopter, searching for one or more potential perpetrators,” the Oslo police department ​said in a statement.

The embassy did not ​immediately ⁠respond to a request for comment outside of regular business hours.

The US State Department did not immediately respond ⁠to ​a request for comment.