Prosecutors in Poland's probe into CIA prison weighing visit to Guantanamo Bay inmates

A Polish prosecutor says investigators have discussed seeking U.S. permission to visit Guantanamo Bay to seek evidence from terror suspects who claim they were held at secret CIA prison in Poland.

Investigators' spokesman Piotr Kosmaty said Thursday that U.S. lawyers for a Yemeni suspect, Walid bin Attash, have discussed with the Poles various ways of obtaining testimony from him, including a visit by the Poles to the Guantanamo Bay detention center where Attash is held.

Poland has sent four requests to the U.S. authorities for assistance in gathering evidence. One has been denied and another denial is expected soon, Kosmaty said.

Without sufficient evidence, Poland may have to end its investigation of whether it hosted a CIA black site where terror suspects were treated harshly.

Polish officials deny it existed.