Lindsey Graham's Death: No New Evidence to Suggest Foul Play, Source

Lindsey Graham's Washington, D.C. home has been crawling with FBI agents since he died ... and, so far, there are no signs something nefarious happened ... TMZ has learned.

Sources with direct knowledge tell TMZ ... "There has been no new evidence to suggest any foul play."

Our sources also say Graham's death falls under the jurisdiction of the Metropolitan Police Department, but the FBI is lending a hand.

We're told ... "MPD is the lead and FBI has offered and provided assistance, as is routine."

As you know, Graham's team announced late Saturday night the Senator passed away after a "brief and sudden illness."

Graham's communications director, Taylor Reidy, later revealed he died from a tear in his aorta.

We got exclusive photos from the scene at Graham's house on Saturday, where D.C. Fire and the EMS Department wheeled him out on a stretcher, seemingly attempting to manually pump oxygen into his lungs.

The Republican Senator's sudden death came as a shock to his constituents and fellow politicians alike, as people flocked to social media to grieve.

TMZ DC got Ted Cruz on Monday ... Cruz was all choked up and fighting back tears over Graham's death.