Experts working to identify the victims of Malaysia Airlines Flight 17 have gathered DNA samples from 283 people and have positively identified 173.

Wim Heijnen of the Netherlands Forensic Institute said Wednesday the DNA samples do not all correspond to a victim's identification. Some of the samples could be from workers who gathered the bodies where the jet was shot down in eastern Ukraine.

All 298 people on board died when the plane heading to Kuala Lumpur from Amsterdam was shot out of the sky on July 17 over an area controlled by pro-Russia separatists.

Scores of forensic experts have been working for weeks to identify bodies and incomplete sets of remains gathered from the scene and flown back to the Netherlands.

"I think that the fact we have gotten DNA profiles in quite a short time from three-quarters of the remains is good. But I am, of course, not satisfied," Heijnen told reporters in The Hague. "We want more DNA profiles from remains and we will carry on to get them. It becomes, understandably, more difficult and sadly more time consuming to do that but taking care is paramount."

Heijnen said he was hopeful that forensic experts can identify more DNA samples using more sensitive equipment or new samples. That process could take weeks or months.

But it remains to be seen if all victims will be positively identified. Fighting and security fears around the crash scene severely hampered efforts to collect bodies and DNA material in the immediate aftermath of the disaster and some remains were burned, making it harder to get positive samples.

"I am not sure we will find 298 identifications, but I hope," Heijnen said. "As long as there is material and there is hope for more identifications, we will continue our work in the laboratories."

Of the 173 sets of remains that have been positively identified, 73 have been returned to next of kin. Police say some families are waiting for more complete sets of remains or until families and friends who were traveling together are all positively identified before reclaiming their loved ones.