Jon Cryer's ex-wife, Sarah Trigger, was interviewed by FBI agents Thursday afternoon.
As we first reported, the FBI is investigating an allegation of a murder for hire plot -- i.e., hitman -- against Cryer, costar of "Two and a Half Men." Someone has told the FBI the plot may involve Jon's bitter custody fight with Sarah.
The threat was taken so seriously last Friday, "Two and a Half Men" was taped without an audience and security poured into the sound stage.
Trigger told TMZ last week she was unaware of any murder for hire plot.
A law enforcement source says the threat has abated, but the investigation is ongoing.