Norwegian police reported on Sunday an explosion near the U.S. Embassy in the capital Oslo, but said there were no casualties.

The explosion occurred around 1 a.m. local time, Oslo police said in a statement, adding they had no information about the blast’s cause or who was behind it.

“A loud bang/explosion was reported at the scene,” Oslo police said. 

Investigators were examining the scene, while dogs, drones, and helicopters were involved in the search “for one or more potential perpetrators,” police said.    

Public broadcaster NRK quoted police incident commander Michael Dellemyr saying the blast hit the entrance of the embassy’s consular section.

“At around 1 a.m. we received several reports of an explosion. We arrived shortly afterward and confirmed that there had been an explosion that hit the US embassy,” he told NRK. “…There is minor damage.” 

Dellemyr told Oslo’s TV2 police would “not comment on anything related to the type of damage, what it is that has exploded and similar details, beyond the fact that there has been an explosion” because “it is very early in the investigation.”

He later told TV2 that police “have an idea of the cause,” adding that “it appears to us that this is an act carried out by someone.”

He said investigators were talking to witnesses, and TV2 reported that a bomb squad was at the scene.

Police said they were in contact with the embassy about the incident and that a large number of resources were on site.

“The police are in dialogue with the embassy and no injuries have been reported,” police added. 

CBS News has reached out to the State Department for comment.

Residents near the embassy said they heard a loud blast. A 16-year-old identified only as Edvard told TV2 that he was watching television when he heard it.

“My mother and I first thought it came from our house so we looked around a little, but then we saw the flashing lights outside the window and a ton of police,” he said. “…There were police dogs and drones and police with automatic weapons and helicopters in the air.” 

U.S. embassies have been placed on high alert in the Middle East over U.S. military operations in Iran, and several have faced attacks as Tehran hits back at industrial and diplomatic targets.

But police gave no indication the incident near the embassy in Oslo was connected to the conflict.