Earlier this week, the FBI raided the Congressman's home and campaign office in Texas as part of the federal investigation.
The report said on Friday, citing a copy of the subpoena, that the US grand jury's probe is seeking records about the Congressman, his wife Imelda Cuellar, and one of his campaign staffers.
The investigation, the report said, appears to be focused on three Texas-based companies which appear to be overseen by Imelda Cuellar. The probe is also looking for records on any US logistics-related firms and cultural advocacy organizations that have ties to Azerbaijan, the report added.
US authorities are specifically looking for records revealing "anything of value" that Congressman Henry Cuellar, his wife, or others close to them may have received from foreign officials or business leaders, the report said citing the subpoena.
Moreover, the report said US authorities are also looking for records of any service, work or favors the congressman or his wife may have done on behalf of foreign officials and companies, or US businesses.
Henry Cuellar, who has served in Congress since 2005, previously served as a co-chair of the Congressional Azerbaijan Caucus and had met with Azerbaijan officials, including Ambassador Elin Suleymanov, the report said.
Henry Cuellar's office said the congressman will fully cooperate in any investigation, according to the report.