It's been called "the forgotten attack" but it's one of the worst terrorist attacks in U.S. history.

Eight years after the USS Cole was attacked by a motorboat packed with explosives, all of the six men convicted of the strike have escaped from prison, or been freed by Yemeni officials.

Seventeen sailors were killed and 40 more wounded in the strike, blamed on Usama bin Laden's al Qaeda network.

Jamal al-Badawi, who helped organize the Cole plot, has reportedly escaped from Yemeni prisons twice. He is supposedly back in jail now, but the Washington Post reported that he has been spotted at his home and is apparently able to come and go around town as he pleases.

Another Cole defendant, Fahd al-Quso, reportedly was freed last year.

Two others, described as main plotters, are being held in held at Guantanamo Bay, Cuba, out of reach of U.S. courts. One other defendant may or may not be in prison in Yemen and the other three others apparently were freed.

Most of those believed responsible were rounded up, put on trial, put in a Yemeni prison. Two years later, most of them tunneled out of prison.

All this frustrates FBI agents who worked the case.

"After we worked day and night to bring justice to the victims and prove that these al Qaeda operatives were responsible, we're back to square one," FBI lead investigator, Ali Soufan told the Post. "Do the [Yemenis] have laws over there or not? It's really frustrating what's happening."

FBI Director Robert Muller flew to Yemen in April, the paper said, to demand that Yemen extradite both men to face charges in New York. So far, Yemen has said no.

Yemeni officials have said that some of the Cole defendants have been let go because they've helped authorities track down other suspected terrorists, or because they've taken part in a "dialogue and reconciliation" program to reform al-Qaeda members.

FOX News' Molly Henneberg contributed to this report.

Click here to read the full Washington Post story.