The National Weather Service has upgraded the deadly tornado that swept across the El Reno area to an EF-5.

On Friday, May 31, five tornadoes touched down in the Oklahoma City metro area, including a massive tornado that hit El Reno.

Complete Coverage: May 2013 Tornado Outbreak

That tornado was originally rated an EF-3. However, the National Weather Service upgraded it to an EF-5 on Tuesday. Experts say it was 2.6 miles wide, which was the widest tornado ever recorded in the U.S. history.

This tornado touched down at 6:03 p.m. Friday, 8.3 miles west, southwest of El Reno, near Courtney Road, about one mile north of Reuter Road.

It lasted for about 40 minutes, before ending 6.2 miles east, southeast of El Reno, near I-40 and Banner Road.

The tornado's path was 16.2 miles.

Wind speeds were measured at 295 miles per hour less than 500 feet above ground, according to the National Weather Service.

Several people were killed as the massive tornado crossed I-40, including a mother and her baby.

Three storm chasers were also killed while they were chasing this tornado.