WARSAW, Poland (AP) — Polish prosecutors investigating the 2010 plane crash that killed President Lech Kaczynski and 95 others say they are seeking help from foreign laboratories in testing the evidence.

The prosecutors are investigating whether anyone contributed in any way to the crash near a military airport in Russia. Poland's ruling party head, Jaroslaw Kaczynski — who is the late president's twin — suggests it resulted from an attack.

In a communique Monday the National Prosecutor's Office said a scientific police laboratory in Madrid, Spain, was "yet another" foreign institution that will carry out forensic tests for them. It will check wreckage samples for traces of explosives. The wreckage remains in Russia.

A separate probe led by Defense Minister Antoni Macierewicz is seeking evidence to back the assassination theory.