The Dutch government has released nearly 600 documents related to the July 17 crash of Malaysia Airlines Flight 17 crash in eastern Ukraine. Investigators made the documents available after local news outlets pressured the government with freedom of information requests, although documents containing private data of the 298 victims will remain classified, the Dutch NL Times reported.

The 575 documents are mainly emails from the National Crisis Core Team, which was established in the wake of the crash to travel to Ukraine and investigate what happened. The Dutch team led the investigation because 193 victims were from the Netherlands. The investigation team was charged with recovering the remains of the victims and discovering what brought the aircraft down.

The Malaysia Airlines flight was brought down while on route from Amsterdam to Kuala Lampur, Malaysia. While theories about how it crashed have been plentiful, the most viable is that pro-Russian rebels using a Russian-supplied BUK missile launcher shot it down. Dutch experts concluded last month after an independent investigation that it was the probable cause of the crash, but the official probe is still ongoing.

The newly released documents contain little about how the crash happened. Those findings will be presented later this year, investigators said.

Most of the documents discuss how the team would communicate with the families of the victims, make condolence registers and carry out national commemorations. However, a number of emails left one potential clue: an oxygen mask that was discovered attached to the body of one passenger. The emails called for forensic tests to discover whether the mask was used or not. If proved that the mask was used, it may give the investigation insight into what happened onboard before the aircraft came down, and potentially dispel other theories.

An expert interviewed by International Business Times last July said that passengers may have died almost instantly if a missile had hit the plane. “It’s a possibility that the passengers on the side that the missile warhead penetrated were killed very quickly,” said Richard Lloyd, a former U.N. weapons inspector and missile technology expert. “The combination of the warhead blast and the shrapnel, which would have traveled at more than 6,000 feet (1,800 meters) per second, will likely be the cause of many of the deaths once forensic tests are taken.”

If this were the case, attaching an oxygen mask in that time would have been very difficult, making the forensic tests vital in coming to a conclusion. 

The preliminary report from investigators says that the aircraft broke up in midair after high-energy objects hit the fuselage.