OKLAHOMA CITY (AP) — Federal regulators have shut down 17 wastewater disposal wells in the Osage Nation of northeastern Oklahoma following a weekend earthquake that matched the state’s strongest on record, state officials confirmed Tuesday.

Because the wells are located on tribal land, Oklahoma regulators have no jurisdiction over oil- and gas-producing facilities in the region.

Oklahoma Corporation Commissioner Matt Skinner told The Associated Press that the U.S. Environmental Protection Agency notified the state Tuesday that 17 wells were ordered closed.

“We’ve never had to do anything that directly involved Osage County, but on Saturday (the EPA) were quick to respond,” Skinner said. “They confirmed on Sunday they were going to put that directive in place, and today they gave us the numbers.”

The 17 wells are located in a 211-square mile area within Osage County, near where a magnitude 5.6 temblor struck Saturday. The epicenter was near Pawnee.

One man suffered a minor head injury in the quake when part of a fireplace fell on him, and emergency management officials said Tuesday they have received reports of damage to at least 11 homes. Oklahoma State University also reported several buildings at the Stillwater campus sustained damage, but all of those were determined by structural engineers to be safe for occupancy.

A regional spokesman for the EPA, Joe Hubbard, did not confirm any details about the wells in Osage County that were shut down, including the volume of wastewater that was being disposed into them. An increase in magnitude 3.0 or greater earthquakes in Oklahoma has been linked to underground disposal of wastewater from oil and natural gas production.

“We are working closely with the state of Oklahoma, the Bureau of Indian Affairs and the Osage Nation to evaluate available information and take appropriate next steps to protect public health and the environment,” Hubbard said in a statement.

A spokesman for the Osage Nation, Jason Zaun, also did not return a telephone message seeking comment on the EPA’s order.

Located across more than 2,300 square miles in northeastern Oklahoma, the Osage Nation Reservation, also known as Osage County, is the largest of the state’s 77 counties. The tribe owns all of the mineral rights, and unlike the rest of the state, the Oklahoma Corporation Commission has no jurisdiction over oil and gas operations there.

“We have no data whatsoever on oil and gas activity in Osage County,” Skinner said. “We don’t know how many (wells). We don’t know how deep. We know nothing about them.”

The Oklahoma Corporation Commission, which since 2013 has asked wastewater-well owners to reduce disposal volumes in parts of the state, already had ordered 37 wells in a 514 square-mile area around the epicenter of Saturday’s earthquake to shut down within seven to 10 days because of previous connections between the injection of wastewater and earthquakes.

Meanwhile, two more earthquakes of magnitude 4.1 and 3.6 rattled northwest Oklahoma Tuesday, in an area away from Saturday’s quake.

The Oklahoma Department of Emergency Management said there were no reports of damage or injuries connected to Tuesday’s quakes.