By Jeremy Herb, CNN

House Democrats on Thursday issued subpoenas to two associates of President Donald Trump's personal attorney Rudy Giuliani who were indicted by federal prosecutors on the same day.

The subpoenas to Lev Parnas and Igor Fruman, the associates working with Giuliani to dig up dirt on former Vice President Joe Biden and his son in Ukraine, come after Parnas and Fruman signaled they would not attend depositions scheduled for this week.

The subpoenas are separate from the indictment, in which federal prosecutors allege that Parnas and Fruman illegally funneled foreign money into US elections.

The leaders of the three House committees leading the impeachment inquiry demanded that Parnas and Fruman turn over documents related to communications with the White House, Ukrainian officials and Giuliani by October 16.

The chairmen argued in a letter to John Dowd — Trump's former personal attorney who is representing Parnas and Fruman — that the Giuliani associates are private citizens and therefore cannot ignore the subpoenas just because the White House isn't cooperating with the probe.

"They are required by law to comply with the enclosed subpoenas. They are not exempted from this requirement merely because they happen to work with Mr. Giuliani, and they may not defy congressional subpoenas merely because President Trump has chosen the path of denial, defiance, and obstruction," wrote Intelligence Chairman Adam Schiff of California, Foreign Affairs Chairman Eliot Engel of New York and Oversight Chairman Elijah Cummings of Maryland.

The subpoenas to Parnas and Fruman add to a rapidly growing list of subpoenas issued as part of the Democratic impeachment inquiry. The committees have sent subpoenas to the State Department, White House, Pentagon and Office of Management and Budget, as well as to Giuliani and US Ambassador to the European Union Gordon Sondland.

More subpoenas are likely in the coming days in response to White House stonewalling of the impeachment probe.

The Democrats wrote to Dowd that they would also be seeking testimony from the Giuliani associates "at a later date." It's unclear whether the indictment will complicate those efforts, as Congress had challenges obtaining testimony from officials who had been charged by former special counsel Robert Mueller before the cases were completed.

The subpoenas request Parnas and Fruman provide documents and communications related to efforts to persuade the Ukrainians to investigate Burisma, the energy company that hired Hunter Biden, as well as the ouster of US Ambassador to Ukraine Marie Yovanovitch, which Parnas and Fruman had pushed for. There's no evidence of wrongdoing of Joe or Hunter Biden in Ukraine.

Dowd wrote the committees earlier this week objecting to the document request, arguing that some materials they were seeking could be protected by attorney-client privilege and that the request was "overly broad and unduly burdensome."

"The subject matter of your requests is well beyond the scope of your inquiry," Dowd wrote, adding that Democrats were trying to "harass, intimidate and embarrass my clients."