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.

At this border town, a point where the Iron Curtain once divided Austriafrom Hungary, the authorities said they were considering stepping up efforts to detect international smugglers. In the absence of a more ambitious European solution, police and politicians were mulling whether to randomly stop cars and trucks to search for illicit human cargo.

By late Sunday, it appeared as if smugglers had caught wind of the possible traps, and they steered clear of the border. Red Cross volunteers, police officers and even some Austrian soldiers had braced for a predicted wave of some 7,000 new arrivals, but by evening they had not materialized.

Normally cars, trucks and vans thread their way through the maze of old Communist border posts and present-day truck stops without being stopped.

The beginnings of that open border came 26 years ago, when thousands of people from Communist East Germany surged past this and other crossing points. Now, the mass movement of people across Europe shows how globalization and digital technology have lured arrivals from further afield — Afghans, Bangladeshis, Iraqis, Syrians and the occasional Iranian.

Many of them have willingly handed off hundreds or thousands of euros to get further on their northward trek — which frequently takes them through Greece, the Balkans and Hungary — to seek asylum in more prosperous European countries, especially Germany.

Late Saturday, the Hungarian police detained one more Bulgarian suspected of being part of the smuggling operation that lead to the deaths. The police said in a statement that they would request pretrial detention, as they have with four others — three other Bulgarians and an Afghan — pending a trial in Kecskemet, Hungary, on Saturday. The officials would not discuss any more details of the investigation.

At least a dozen people suspected of attempting to smuggle migrants through the country in decrepit vans were also detained over the weekend.

In the meantime, the flow of migrants entering Hungary by the thousands from Serbia has not slowed, despite the completion of a barbed-wire barrier, with a higher fence still being constructed.

It became apparent over the weekend that the 71 were not alone in being packed tightly into the backs of trucks and vans, driven without adequate air flow or relief despite a heat wave. Temperatures were as high as 98 degrees Fahrenheit in eastern Austria this weekend.

The police said Saturday that three children were found severely dehydrated early Friday in a truck at Austria’s border with Germany, near Passau. But in a sign of the desperation of the asylum seekers, the parents of the children whisked them out of the hospital where they had been taken on Friday and then disappeared.

Mahmoud Otri, 23, from Aleppo, Syria, said Sunday that it was only after a similar journey of his own that he learned of the tragedy involving the 71 migrants.

“We were close to being like them,” he said as he recounted a careening 10-hour drive from southern Hungary to just short of the border here.

Mr. Otri, who spoke English and gave a detailed account of his journey from Aleppo to Hungary via Turkey, Greece, Macedonia and Serbia, said during that last stage he was in a small truck crammed with about 50 others, including at least four women and three children.

They were so cramped that most men stood, he said, while women, children and some other males could only kneel. By the time they neared Austria, they were gasping for air.

One of the Afghans on board had a knife, which Mr. Otri said he had earlier used to intimidate some of the Arabs — Syrians, Iraqis and one Lebanese — on board. But the Afghan used it to cut a hole in the roof of the small truck. “We were close to death,” Mr. Otri said.

He paid 1,500 euros for his passage, which he said was arranged after complex negotiations took him to the northern Serbian border town of Subotica, then back to a Belgrade hotel and again to Subotica. From there, his group of about nine was taken to a “point” in the forest, he said, where they waited one night.

Hungarian police officers combing the border apparently forced their guide — who Mr. Otri said was part of the “service” provided by smugglers — to move the group to another spot, where they waited two nights, Mr. Otri said. He added that he had been in his fourth year of studying engineering in Aleppo but decided two months ago to flee the war-torn home.

“There is no life in Aleppo,” he said, as he and a fellow native of the city named at least four militias they said were battling in the area.

“There is no future there for 10 years,” said one young man. Mr. Otri corrected: “Twenty.” The men then agreed that Aleppo would be fortunate if it recovered even in that time.