Congressional Democrats are preparing to intensify their inquiry into deals that nine major law firms struck with the Trump administration, with Sen. Richard Blumenthal warning that subpoenas are an option if the firms do not provide the information lawmakers want.

“I hope they’ll cooperate. If they don’t, we’ll consider using all of the tools at our disposal, including subpoenas,” the Connecticut Democrat told reporters, according to Bloomberg Law.

The agreements have drawn scrutiny in Congress since the firms pledged a combined $940 million in pro bono legal work. Lawmakers have sought details about why the firms entered the deals and what the agreements required of them, but the firms’ responses so far have done little to satisfy investigators, according to Above the Law.

The firms involved are Paul Weiss, Skadden, Kirkland & Ellis, Latham & Watkins, Cadwalader, Willkie Farr & Gallagher, Simpson Thacher, Milbank, and A&O Shearman. Their collective pledge of free legal work is central to the congressional inquiry.

Blumenthal’s comments signal that Democrats, having gained subpoena power, may move beyond requests for voluntary cooperation. He did not say that subpoenas had already been issued. Rather, he identified them as one of the tools lawmakers could consider if the firms do not supply further information.

The prospect of compelled testimony or documents raises the stakes for the firms as lawmakers continue to examine the circumstances surrounding their agreements with the administration. At issue for investigators are both the firms’ reasons for making the deals and the obligations they accepted as a result.

The firms have already provided responses to Congress, but those responses have not resolved lawmakers’ questions. Whether the firms choose to disclose more voluntarily could determine whether Democrats pursue the compulsory measures Blumenthal described.

For now, the senator’s message leaves the next step open: cooperation from the firms could provide investigators with the details they are seeking, while continued dissatisfaction could prompt lawmakers to consider subpoenas.