Two top Republican senators are asking Attorney General William Barr to look into text messages between former FBI agent Peter Strzok and former FBI lawyer Lisa Page that suggest that shortly after the 2016 election, the FBI wanted to develop sources within the incoming Trump administration for surveillance purposes.

Sens. Chuck Grassley (R-IA) and Ron Johnson (R-WI) wrote in a letter to Barr on Thursday:

[I]n the course of our oversight work we have reviewed certain text messages that may show potential attempts by the FBI to conduct surveillance of President-elect Trump’s transition team. In text messages exchanged between former FBI Special Agent Peter Strzok and former FBI Attorney Lisa Page, the two discussed the possibility of developing ‘potential relationships’ at a November 2016 FBI briefing for presidential transition team staff.

While discussing who should attend the briefing, Strzok texted Page on November 17, 2016: “If Katie’s husband is there, he can see if there are people we can develop for potential relationships.”

Grassley and Johnson wrote that the nature of the communications and the precise purpose of any attempts to “develop relationships” with Trump or Pence transition team staff “are not immediately clear.”

“Were these efforts done to gain better communication between the respective parties, or were the briefings used as intelligence gathering operations? Further, did any such surveillance activities continue beyond the inauguration, and in the event they did, were those activities subject to proper predication?

“Any improper FBI surveillance activities that were conducted before or after the 2016 election must be brought to light and properly addressed,” they wrote.

Barr is examining whether the FBI had proper predication for launching an investigation into the Trump campaign in July 2016 amid suspicions it was colluding with Russia to obtain and release hacked Democrat emails.

The senators also asked Barr to examine leaking of sensitive material by FBI personnel to the media.

“Leaks to the media about ongoing investigations undermine the ability of investigators to properly investigate. Moreover, sensitive leaks to the media while members of congress performing constitutionally mandated oversight are kept in the dark is unacceptable,” they wrote.

They asked for Barr to brief them by May 9 on his efforts to look into whether the Obama administration spied on the Trump campaign in 2016.

Earlier this month, Barr testified to the Senate Appropriations Committee that he thought “spying did occur.”

“Yes, I think spying did occur,” Barr said during the hearing. “But the question is whether it was predicated — adequately predicated, and I’m not suggesting that it wasn’t adequately predicated, but I need to explore that. I think it’s my obligation.”

Fox News first reported that the text messages between Strzok and Page — who were involved in an extramarital affair — were under renewed scrutiny, in light of Barr’s efforts.

Trump responded to those text messages Thursday on Fox News’s Hannity.

“They were trying to infiltrate the administration,” Trump said. “Really, it’s a coup. It’s spying. It’s hard to believe in this country we would have had that.”

Rep. Devin Nunes (R-CA) said the text messages were further evidence that the FBI’s investigation of the Trump campaign “was filled with irregularities.”

“The more we discover about the true origins of the investigation, the more abnormal it appears in every conceivable way,” he said.