There were a few new faces at the site on Thursday. Three Australian investigators worked in the field, joining three Malaysians. Before departing Thursday, the Malaysians said that they were surprised at the amount of access they had to the site and that they felt safe, Mr. Bociurkiw said.

There have been widespread reports of looting, but Mr. Bociurkiw said his monitoring group, which has now spent more time at the site than any other, had not seen any. The Malaysians said they had seen valuables in the fields untouched, he noted, including a bottle of duty-free perfume, auto parts, backpacks full of belongings, a watch and some jewelry.

The Dutch Safety Bureau said in a statement that an initial examination showed that both of Flight 17’s so-called black boxes had been damaged, but that their memory chips were intact. The bureau added that there was “no evidence or indications of manipulation” of either the cockpit voice recorder or the flight data recorder, and that the data from both had been downloaded by experts from Britain’s Air Accidents Investigation Branch in Farnborough, England.

The cockpit voice recorder normally contains the last two hours of pilot conversations and other cockpit sounds, including any alarms that would have sounded as the plane’s flight systems failed. The data recorder tracks hundreds of different statistics, including the plane’s position, speed, altitude and direction. The Dutch board said the data from both recorders would be synchronized and analyzed, but it did not indicate when it expected to make their findings public.

The Dutch board said it was confident that both the black boxes and the debris on the ground would yield “sufficient relevant information” to determine the circumstances of the crash. But as is common with technical inquiries, investigators said their aim would not be to apportion blame.