DALLAS (AP) — A Texas lawyer says he found a tracking device on his pickup truck during an escalating court battle with a businessman at the center of an FBI investigation into Attorney General Ken Paxton.

In a court filing Monday, Steve Lemmon offered no evidence of how the tracker came to be on his truck and acknowledged not knowing who put it there. But he said “the surveillance clearly appears to be tied to” his case with Nate Paul and that trackers were also found by other people whom the real estate developer sees as “business adversaries.”

It is generally a crime for anyone other than law enforcement to put a tracker on someone else’s vehicle in Texas. While the devices’ origins are unclear, their discovery adds espionage-tinged intrigue to the imbroglio around Paxton and Paul, the embattled developer whom the Republican is accused of breaking the law to help.

A person familiar with the matter said the FBI is investigating the origins of the tracking devices. The person spoke on condition of anonymity because the investigation is ongoing. The FBI declined to comment.

Paul’s lawyer, Michael Wynne, called the suggestion that his client had something to do with the devices “shocking.” During sworn testimony last year, he objected and told Paul he did not have to answer many questions, including ones about trackers.

“I have absolutely no reason to believe that Mr. Paul would have anything to do with anything like that and would expect Mr. Lemmon to have sound proof before he makes that kind of inflammatory allegation,” Wynne told The Associated Press.

Lemmon, who declined to comment, said in the court filing that the FBI has “custody” of the device found on his truck. He did not name the other people he says found trackers.

Paul has been under FBI investigation since at least 2019. Last year, he launched a campaign of counter allegations against the agents, federal judges and others, including Lemmon’s client. Paxton hired an outside lawyer to investigate these claims in September, prompting eight of his top deputies to report him to the FBI, which then opened a probe into Texas’ top lawyer.

Paxton has broadly denied wrongdoing. His defenses attorney, Philip Hilder, declined to comment when asked about the tracking devices Monday.

Keith Byers, an attorney in the Houston area who previously oversaw FBI public corruption cases, said illegally installing trackers would be unusual in the U.S., even for street gangs and drug cartels.

“Anyone who resorts to installing illegal tracking devices on the vehicles of their adversaries is either highly motivated, desperate, unstable, or completely oblivious to the consequences,” Byers said.

Paul, who employs a woman with whom Paxton allegedly had an extramarital affair, is facing lawsuits from creditors and disgruntled business partners around the country.

Among his legal challenges is a long running suit from an Austin nonprofit that has a financial stake in Paul’s business. Lemmon represents the court-appointed overseer for some of Paul’s companies and has played a significant role in the contentious litigation.

Lemmon disclosed finding the tracking device in a quarterly report the overseer filed in the Roy F. and Joann Cole Mitte Foundation’s lawsuit.

Last summer, Paxton’s office intervened in that case, a move some of his deputies said in a whistleblower lawsuit was inappropriately aimed at forcing a resolution in Paul’s favor. Several weeks later, Paxton hired a Houston defense attorney to investigate Paul’s uncorroborated claims that Lemmon’s client and the foundation’s lawyer were part of an elaborate conspiracy to steal $200 million worth of Paul’s properties.

Wynne said Lemmon’s claims about the tracking devices “are another attempt to distract from the fraudulent financial scheme.” Lemmon has dismissed Paul’s allegations as “ludicrous.”

The lawyer Paxton hired to investigate the developer’s claims was a 2015 law school graduate with no prosecutorial experience and connections to Wynne.

Paxton dropped the investigation in October after the bribery and abuse-of-office accusations against him became public. Six days later, Lemmon said, a mechanic found the tracking device while doing routine maintenance on his truck.

Lemmon said the FBI still has the tracker and that agents requested to meet with him, his client and his law partner the week after he found it. At the meeting, Lemmon said, they learned that Paul had asked Paxton to investigate the developer’s conspiracy claims.

Two weeks later, Lemmon questioned Paul about tracking devices under oath. He asked a series of questions about whether Paul ever had investigators put a tracker on the vehicle of anyone involved in a court case with him, according to a transcript of the deposition obtained by the AP.

Wynne said the questions were irrelevant to the case, as well as “harassing and insulting.” He told Paul he did not have to answer.