Three of the seven tornadoes that struck Oklahoma and killed 10 people this week have been upgraded from EF-3 to EF-4. A fourth tornado has now been rated an EF-2.
An EF-4 tornado has wind speeds of 166 to 200 mph and is the second highest rating for tornadoes.
The weather service on Friday said EF-4 tornadoes were produced Tuesday from one storm that stretched from Binger to Guthrie, a second from Chickasha to near Moore, and a third from Washington to Goldsby.
An EF-3 tornado with winds between 136 and 165 mph occurred at Canton Lake and the EF-2 twister struck near Stillwater.
Tornadoes near Stella and Ravia have not yet been rated.
The weather service said it's still investigating the storms and the ratings may again be updated.