A Republican House chairman is threatening to subpoena state attorneys general and green groups for information on their probes into Exxon Mobil Corp. in an escalation in the ongoing fight over their climate change-related investigations.

In Wednesday letters to New York Attorney General Eric Schneiderman, Massachusetts Attorney General Maura Healey and a handful of environmental groups, Science Committee Chairman Lamar Smith Lamar Seeligson SmithOVERNIGHT ENERGY: Cheney asks DOJ to probe environmental groups | Kudlow: 'No sector worse hurt than energy' during pandemic | Trump pledges 'no politics' in Pebble Mine review Cheney asks DOJ to probe environmental groups How effective are protests and riots for changing America? MORE (R-Texas) said his panel “will consider use of compulsory process to obtain responsive documents in the possession, custody, or control of your office” should they not respond to the letter.

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“If you continue to refuse to provide information responsive to the Committee’s requests on a voluntary basis, I will be left with no alternative but to utilize the tools delegated to the Committee by the Rules of the House of Representatives,” Smith added in the letters.

Smith has twice asked Schneiderman, Healey and other state or territory attorneys general to turn over documents related to their investigations into claims Exxon lied to the public and shareholders about what it knew about climate change decades ago.

His request — originally sent in May — asks for copies of communications between their offices and several green groups, among other things. Smith’s Wednesday letters are the first to raise the possibility of a congressional subpoena related to the probe.

The attorneys general have resisted Smith's request, saying it oversteps Congress’s investigative power. They say their investigations center on potential fraud on Exxon’s behalf, not protected speech, as the company and its supporters allege.

“The First Amendment does not give any corporation the right to commit fraud,” Schneiderman said in a statement after Smith sent his second request for documents last month.

“Everything we’ve seen this week is ripped straight from the Big Tobacco playbook: delay, deflect, and distract from any serious investigation into potential fraud or corporate malfeasance.”

In his Wednesday letter, Smith said the attorneys general requests are too broad to be focused on fraud alone, noting their request for documents related to Exxon’s communications with outside think tanks, researchers and others.

“Protecting the ability of these scientists — and all scientists — to conduct research uninhibited by the potential adverse effects of investigations by law enforcement is a goal of this Committee.”

The fight between the Science Committee and the attorneys general is one front in an ongoing legal fight over Exxon’s climate research.

The company has recently secured two victories in that battle: Claude Walker, the attorney general of the U.S. Virgin Islands, last month withdrew his subpoenas sent to Exxon and a right-wing think tank, and Massachusetts Attorney General Maura Healey (D) has recently agreed to not enforce a demand for documents while Exxon challenges it in court.