(CNN) -- A federal judge determined Wednesday that Shannon Richardson, an actress accused of sending ricin-laced letters to President Barack Obama and New York Mayor Michael Bloomberg, is a "flight risk" and thus must remain behind bars.
The Texas woman, also known as Shannon Rogers and Shannon Guess, was arrested in June. She was ordered to undergo a mental evaluation, and late last month, she was found competent to stand trial.
The actress has pleaded not guilty on all counts.
Richardson was in a federal court in Texarkana, Texas, for a roughly 30-minute detention hearing Wednesday morning.
According to a court document, her lawyer and prosecutors both presented their arguments as to why she should be allowed to go free on bail or, conversely, why she should remain in custody.
Judge Caroline Craven concluded that, although Richardson probably isn't "a danger to the community," she is "a serious flight risk, and no conditions will ensure her appearance."
As a result, Craven ordered the 35-year-old to remain detained pending her trial.
Three envelopes containing the natural, highly toxic compound derived from castor beans were mailed from Shreveport, Louisiana, in May. They were discovered, before causing any injuries or fatalities, with what the FBI described as "very low concentrations" of ricin.
Richardson -- who has had minor roles in television series including "The Walking Dead" and "The Vampire Diaries" -- initially told FBI agents that her now-estranged husband Nathaniel had sent the ricin-tainted letters.
But, authorities have said, Richardson was found to be "deceptive" in a polygraph exam.
Investigators found that her computer storage devices contained the text of threatening letters sent to the president. But the couple's computer records show that her husband couldn't have printed them out because he was at work at the time, according to an FBI arrest affidavit.
Eventually, Richardson admitted to investigators that she'd mailed the letters, though she claimed her husband had typed them out and forced her to print and mail them, the affidavit said.
Nathaniel Richardson denied doing any such thing, telling investigators that his wife was "intentionally misleading" them and that she'd wanted to end their marriage and leave them, court papers said.
He filed for divorce in June, and court papers indicated that Shannon Richardson was pregnant.