As of the time of this report, Ryan Lee's Twitter account makes no mention of his signing, but it's possible the tweet was deleted. Steelers Depot did not link the tweet or post a screenshot of it.
Because it seems possible he was told to take it down due the fact players aren't technically allowed to sign until noon ET, and the tweet came before that, we're passing the report along.
Besides, it wouldn't be shocking for Lee to sign. He made an impression in camp and four preseason games, and looks like a player who could develop into a regular along the offensive line, much like Doug Legursky and Ramon Foster have (other undrafted offensive linemen, like Lee).
The web site also cited a source in reporting LB Marshall McFadden will also be signed to the practice squad.