Media playback is unsupported on your device Media caption The BBC's David Shukman looks at the task ahead for the pathologists and crash scene investigators

UK investigators are continuing to examine black box flight recorders from downed Malaysian Airlines flight MH17.

The Air Accidents Investigation Branch (AAIB) has downloaded "valid data" from the cockpit voice recorder (CVR).

The AAIB in Farnborough is thought to be examining the flight data recorder (FDR), which records technical data.

Two more planes carrying victims have arrived in the Netherlands. All 298 people on MH17 died when it crashed in east Ukraine last week.

Many of those travelling on the flight from Amsterdam to Kuala Lumpur were Dutch.

There were 10 Britons on board.

British accident investigators were tasked with retrieving data from the black box recorders following a request by authorities in the Netherlands.

Solemn ceremony

All the bodies are being flown into Eindhoven and taken to the Korporaal van Oudheusden barracks, south of the city of Hilversum, for identification - a process that could take months.

Media playback is unsupported on your device Media caption Anna Holligan reports from a military airbase in Eindhoven

Forty coffins were received from two military planes in a solemn ceremony at Eindhoven air base on Wednesday.

On Thursday, two planes transported 51 bags containing bodies or body parts from Ukraine to the Netherlands.

Analysis

Image copyright Reuters

Jonathan Sumberg, BBC transport reporter

Why are the black boxes being examined in the UK? The British Air Accidents Investigation Branch (AAIB) says it is one of only two so-called "replay units" in Europe with the necessary equipment to listen to what has been recorded on the cockpit voice recorder.

They have the kit to analyse in minute detail what can be heard in the last few minutes of flight MH17. The information is incredibly sensitive so investigators gather in a sealed room so that only those who should be listening can listen.

There are four speakers on the walls creating a surround sound - anything to help the investigators hear exactly what went on. They may even hear any explosion.

Investigators say that, depending on the extent of the damage, they can retrieve information from the boxes within 24 hours.

The black boxes were transported to the UK after pro-Russian rebels handed them to Malaysian officials this week.

The Dutch Safety Board, which is leading the investigation, said "valid data" had already been downloaded from MH17's CVR which will be "further analysed and investigated".

The board said: "The CVR was damaged but the memory module was intact. Furthermore no evidence or indications of manipulation of the CVR was found."

Replay units

On Wednesday, a spokesman for the Department for Transport said data from the two devices would be downloaded and sent back to Dutch investigators.

Depending on damage to the black boxes the process should take about two days, the spokesman said.

What happens now?

The Air Accidents Investigation Branch (AAIB)'s data and cockpit voice recorder analysis laboratories are one of only two places in Europe with the state-of-the-art equipment necessary to analyse the black boxes. The other being in France.

They have been designed to eliminate electromagnetic interference during the replay of the recordings, and are soundproofed using special glass to ensure the information stays private.

Four speakers placed in each corner of a room will have been used to create a surround-sound playback from the cockpit voice recorder black box.

This will allow the investigators to hear whether the cockpit would have heard an explosion and/or the sound of shrapnel peppering the area, which would have been created by the missile hitting another part of the aircraft.

It could also inform the team how long the plane kept flying, or whether it immediately broke apart.

Other equipment will be used to analyse the information taken from the data recorder black box, which would have recorded about 2,000 flight parameters.

Jets downed

On Tuesday, Whitehall sources said information has emerged from Ukrainian intercepts suggesting that crash evidence was deliberately tampered with.

The sources said this included moving bodies and scattering the parts of other aircraft among the wreckage of the downed Malaysia Airlines plane.

Media playback is unsupported on your device Media caption The BBC's Fergal Keane at the crash site: "When we arrived, there were no guards"

Intelligence has been obtained which strongly indicates that the plane was shot down by an SA-11 BUK missile launched from a separatist-held area in eastern Ukraine.

Western leaders have accused Russia of arming separatist rebels in Ukraine.

Russia has suggested Ukrainian government forces are to blame.

Meanwhile, as fighting continued in eastern Ukraine on Wednesday, officials in Kiev told the BBC that two aircraft, thought to be military jets, had been downed just 35km (20 miles) from the crash site.