(AP) — The Oklahoma medical examiner’s office says eight of the 20 people killed during last Friday’s tornadoes and subsequent flooding either drowned or probably drowned.

The agency said Wednesday that one person died of asphyxiation and 10 died as a result of blunt force trauma or head injuries. The cause of death was not yet determined for one victim.

Storms that swept through the Oklahoma City area on Friday generated an EF5 tornado and violent flash floods. The tornado was the widest one ever recorded at 2.6 miles.

Oklahoma emergency officials have said many of those who drowned were swept away while taking shelter from the tornado in storm drainage ditches.