The bodies of 71 people were in a lorry that was found abandoned in Austria on Thursday, police have said.

When police were first alerted to the 7.5 ton truck, the corpses were said to be so decomposed it was difficult to put an estimate on the number of dead.

It was originally thought there were between 20 and 50.

Investigators have been examining the lorry in detail in order to work out how many were inside.

An Austrian police chief said that several were refugees from Syria.

Hans Peter Doskozil, police chief for the province of Burgenland, said he believes the truck was parked up for at least 24 hours before it was discovered.

Three people have now been arrested in Hungary in connection with the deaths.

They earlier said they believe a Bulgarian-Hungarian trafficking ring is responsible and they hope the arrests will lead them to those behind the deaths.

Of those arrested in Hungary, three are Bulgarian and a fourth is of Afghan nationality.

A statement on Hungary Police's website said: "In addition, police have conducted house searches ...and questioned almost 20 people as witnesses".

As yet, none of those arrested are Hungarian, the statement added.

Irish Times reporter Derek Scally is in Austria, and told Newstalk Lunchtime the people inside the truck faced a grim death.

Police said 59 of those who died were men, eight were women and four were children, including one baby girl.

Forensic specialists clad in white protective suits have been seen wheeling body bags away from the refrigerated customs building in the village of Nickelsdorf where the vehicle was taken.

It was found shortly before noon local time (11am UK time) by an Austrian highway patrol which had spotted the vehicle on the edge of the A4 highway, close to Parndorf.

The spot is about 50km (28 miles) southeast of the capital Vienna and about 25km (16 miles) from the Hungarian and Slovak borders.

Austrian newspaper Krone said that early investigations have found the truck was in Budapest in the early hours of Wednesday and was seen at the border at around 9am.

The truck was then seen again in Austria at around 5am on Thursday and when it failed to move for some time, witnesses called the police.

When officers arrived they found the back door slightly ajar and inside were the partially decomposed remains of the migrants.

"When they checked they found it had no driver and blood was dripping out of the vehicle and there was a smell of dead bodies," Helmut Marban, press officer for Burgenland police, said.

The police chief said it is suspected that those trapped in the trailer suffocated after being unable to get out. Post mortems are being carried out to determine the exact causes of death.

Krone is reporting that there is a damage to the side of the lorry that indicates the migrants attempted to break out. Police suspect those responsible have already fled the country.

It comes as a Romanian man was arrested in Hungary for driving a different van that overturned on the M5 highway injuring 10 of the 18 migrants inside.

German Chancellor Angela Merkel said the discovery of the truck in Austria had shaken European leaders discussing the migrant crisis at a Balkans summit.

She said: "We are of course all shaken by the appalling news. This reminds us that we must tackle quickly the issue of immigration and in a European spirit - that means in a spirit of solidarity - and find solutions".

Lindsey Hilsum is international editor with Channel 4 News, and was at the scene yesterday.

She spoke to Newstalk Breakfast earlier.