Updated

Norwegian oil company Statoil says it may have relied too heavily on Algerian military protection at its Ain Amenas gas facility, which was attacked by armed terrorist in January.

In a report on the incident, Statoil says "there is reason to question the extent of their reliance on Algerian military protection."

An al-Qaida-linked militant group stormed the facility, jointly run by BP, Statoil and the Algerian state company on Jan 16. In the ensuing standoff with Algerian forces 40 workers were killed, along with 29 militants.

Torgeir Hagen, who headed Statoil's investigation, said Thursday the assault was "unprecedented."

He says Algerian troops couldn't "prevent the attackers" and security measures failed "to withstand or delay an attack of this scale, and relied on military protection working effectively."