The bomb used to attack the Norwegian prime minister’s office in Oslo on Friday was some kind of Oklahoma City-type device made of fertilizer and diesel fuel, according to an Oslo police official.

Associated Press reported that it is unclear what kind of detonator that bomb had, but that it was stored in a panel truck. Upon detonation, the explosion killed seven people.

The twin attacks in Norway have thus far killed at least 91 people. Oslo police have arrested Anders Behring Breivik, a 32-year-old Norwegian man who is described as a Christian fundamentalist.

The bombing of Oklahoma City in April 1995 which killed almost 170 people was caused by a 4,000-pound fertilizer-and-fuel-oil bomb that was set off in front of a federal building.

The principal perpetrator of that attack, Timothy McVeigh, was later executed.