An explosion struck the US Embassy in Oslo, Norway Sunday morning, causing minor damage to the facility and no reported injuries.

The blast, which struck around 1:00 a.m. local time, occurred at the entry to the consular section, according to police spokesperson Mikael Dellemyr in a statement to public broadcaster NRK. 

"We've determined that an explosion ​hit the American embassy," he said. 

Police separately said that they don't have any idea what caused the blast or who was involved.

"The police are in a dialogue with the embassy and there ​are no ​reports of ⁠any injured persons," they said in a statement.