A federal judge in Texas canceled a hearing Monday in which Exxon Mobil attorneys would have been able to question a leading Democratic state attorney general targeting the company in a case regarding the oil giant's record on climate change.

Texas Judge Ed Kinkeade issued an order Monday canceling the deposition without explanation. The deposition was scheduled for later this week between Massachusetts Attorney General Maura Healey and Exxon's lawyers.

Healey is part of a group of Democratic state attorneys general investigating news reports that Exxon covered up reports by its own scientists in the 1970s because they showed manmade climate change would have a serious impact on the company's business.

Healey and New York Attorney General Eric Schneiderman have been pursuing the company with subpoenas, asking it and various conservative groups that have supported it for all records and emails regarding climate change going back decades.

Exxon has said the investigation is baseless and has called on federal judges in Texas and Massachusetts to issue injunctions to stop the subpoenas, arguing that they are an imposition on the company's right to free speech. Exxon said the company accepts that climate change is occurring and endorses the use of a tax on carbon dioxide to combat it. Many scientists blame carbon dioxide and other greenhouse gases emitted from burning fossil fuels for driving manmade climate change.

The attorneys general are attempting to build evidence for a much broader case against Exxon, showing that it lied to shareholders and the public by withholding its scientists' climate change analysis.

Healey's office celebrated the deposition being canceled. "We are pleased that the federal judge has canceled this unprecedented deposition order," said her spokeswoman, Chloe Gotsis. "Our office has argued strongly that the Texas court has no jurisdiction over our investigation and we will continue to urge it to dismiss Exxon's lawsuit against us."

Environmental groups were much more blunt in their remarks, saying that Exxon's case against Healey has been "fueled by its own paranoia," according to Jamie Henn, a spokesman for the group 350.org, a leading anti-fossil fuel group leading the charge to shift the nation from fossil fuels to 100-percent renewable energy.

"These are the actions of a guilty party, attacking public officials and environmental groups instead of owning up to its own record," Henn said.

The judge's decision came amid reports that President-elect Trump is considering making Exxon CEO Rex Tillerson his secretary of state, which a number of environmental groups said would be a mistake because of the company's harmful record on environmental issues.

"As head of the State Department, Tillerson would have the ability to shape foreign policy to enrich himself and Exxon at the expense of people and environment," said Erich Pica, president of Friends of the Earth. "Tillerson and Exxon have a long history of funding climate denial and causing environmental catastrophes like the Exxon Valdez."

"Having Exxon Mobil's CEO run the State Department would be the ultimate bad deal for Americans and our climate," Pica said.