Police are looking for one or more perpetrators, but no suspect has been arrested, said Frode Larsen, head of the investigation and intelligence unit, at a press conference at Oslo Police Station at lunchtime.
When asked directly whether it was an act of terrorism, Larsen replied:
One of the hypotheses is that it is a case of terror, but we have not completely locked ourselves in. We are open to the possibility that there may be other reasons for what has happened.
According to Larsen, it was some kind of explosive object that had been detonated.
Security initiatives
Police operations chief Grete Metild did not want to comment on the security measures around the U.S. Embassy:
"I can't go into more detail about that. There are various security initiatives,"
she said, adding that she would not provide information about security arrangements.
She was also asked if it was a hand grenade.
We haven't said anything about what was thrown. It was an explosive object, beyond that we won't say anything more.
Police were alerted to the explosion at 1 a.m. Sunday. Dog patrols, a helicopter and drones have been involved in the search for the perpetrators.
The explosion occurred at the consular entrance and caused minor damage. No one was injured and there is no danger to the public.
Security level not increased
The Norwegian Security Police Kripo is cooperating in the investigation, but Norway has not increased the security level.
"The police take incidents in public places very seriously and are investigating the case with significant resources," the police said in a statement.
All events in Oslo will be held as planned on Sunday, the police announced at the same time.
