NICKELSDORF, Austria — Investigators continued to work their way on Sunday through a truck that carried 71 migrants to their deaths last week, removing articles of clothing and bagging and labeling them as possible evidence in an inquiry against the smuggling operation believed to be responsible.

The truck was brought here after the police discovered it on the side of an Austrian highway, the decomposing bodies crammed against one another in a back compartment. One passenger’s Syrian passport was found, leading the authorities to believe that at least some had fled the war there.

Autopsies are expected to be completed by midweek, according to law enforcement officials. The 26 done so far have not yielded any positive identification of the bodies, the Austrian public broadcaster reported.

On Sunday, the authorities in Hungary announced a fifth arrest in the case, which has shocked Europe and highlighted the proliferation of highly organized smuggling operations responding to the wave of migrants from war-torn and turbulent spots in the Middle East and Northern Africa.