Deaths reported after explosion at Longview paper mill in Washington state

Several people are seriously injured and an unknown number have died after an explosion at a paper mill in Longview, on the border between Washington and Oregon.

Neither the mill owner nor the police have released detailed information about how many people have been affected, but "several" people are missing, NBC News reports.

Governor Bob Ferguson has expressed grief over the deaths on social media while rescue efforts are still ongoing.

The explosion was reportedly caused by the implosion of a tank filled with chemicals for bleaching paper pulp.