TULSA, Okla. (AP) — Oklahoma's former lead seismologist says he felt pressured by a University of Oklahoma official to not link the state's surge in earthquakes to oil and gas production.

Austin Holland's sworn testimony came last month as part of a lawsuit filed in 2015 by Prague resident Jennifer Cooper against two oil companies for damages sustained during an earthquake in 2011, the Tulsa World reported . The 5.7 magnitude quake that hit the Prague area, about 50 miles (80 kilometers) east of Oklahoma City, was the largest in state history.

University President David Boren disputed Holland was ever pressured by the school.

Researchers have linked the spike in the number of earthquakes in parts of Oklahoma, Kansas, Texas and other states to the underground disposal of wastewater from oil and gas production. Holland said he was reprimanded for helping publish a peer-reviewed journal article on how to cope with such earthquakes.

When asked by the plaintiff's attorney who pressured him to avoid linking the 2011 quake with wastewater injection wells, Holland said Larry Grillot, the former dean of the university's Mewbourne College of Earth and Energy, and a former director of the Oklahoma Geological Survey influenced or altered wording in his research or presentations.

Grillot denied the accusation, telling the newspaper: "If Dr. Holland is asserting that he received pressure from me to alter his research or conclusions, that's not true. ... That did not happen." Multiple attempts by the newspaper to reach the former Oklahoma Geological Survey official were unsuccessful. The survey is a state agency administered by the university.

Holland also detailed a meeting that allegedly took place with Boren and Harold Hamm, a billionaire oilman who has given millions of dollars to the university. Holland said he was called into Boren's office after he wrote the paper.

Holland said Boren "expressed to me that I had complete academic freedom, but that as part of being an employee of the state survey, I also have a need to listen to, you know, the people within the oil and gas industry."

Holland testified that Hamm told him "to be careful of the way in which I say things, that hydraulic fracturing is critical to the state's economy in Oklahoma, and that me publicly stating that earthquakes can be caused by hydraulic fracturing was — you know, could be misleading, and that he was nervous about the war on fossil fuels at the time."

Boren has said the university was never compromised by Hamm or any other donor and that researchers weren't pressured to change or slow their research. The Tulsa World reported that its attempts to reach Hamm for comment were unsuccessful.