BISMARCK, N.D. (AP) - North Dakota's booming oil patch is sweeping south as speculators explore a reservoir similar to one that has flooded that state with money and jobs.

And that could mean South Dakota soon gets a piece of the oil action.

The Associated Press has learned a flurry of recent leasing activity in South Dakota is tied to hopes for the Tyler Formation, which spans parts of both states. A North Dakota state geologist says it might hold up to one-third the volume of oil estimated in the prolific Bakken shale formation.

The prospect has spurred excitement - and worry - in both states. While the Bakken boom has helped North Dakota economically, it's also brought more traffic and high housing costs. Some South Dakota officials say they hope to be prepared.