Anna Nicole Smith Investigated in Murder Plot to Kill E. Pierce Marshall

Anna Nicole Smith was investigated by the FBI over a possible murder plot to kill her tycoon husband's son E. Pierce Marshall, as they battled for his late father's oil wealth, according to newly released documents.

The documents say Smith was investigated in 2000 and 2001 for her possible role in a murder-for-hire plot against Pierce Marshall - the son oil tycoon J. Howard Marshall II.

During the investigation, authorities confiscated a couple of weapons from Anna's home including a .357 revolver and a 3.5 inch stainless steel knife.

The records say, Smith "began crying and denied ever making such plans," when she was questioned by the FBI.

The investigation was called off in 2001, as there was "insufficient evidence to establish that there was a murder-for-hire plot by Anna Nicole Smith to kill E. Pierce Marshall."

The younger Marshall died of natural causes in 2006. Smith died a year later at age 39, from a drug overdose.

Smith was 26 when she married the 89-year-old Marshall, owner of Great Northern Oil Co. His wealth was estimated by Forbes to be $550 million in 1992. They met while she was a topless dancer at a Texas strip club.

He died of natural causes in 1995, little more than a year after they married. His death triggered a legal battle over his estate between Smith and his son. The Supreme Court ruled unanimously in 2006 that Smith could pursue her late husband's fortune.