Almost three months on from the deaths of 16 prized polo ponies in the back of a truck that travelled across Bass Strait, there are growing calls for authorities to release information.

The ponies, from the Willo Polo club in New South Wales, perished somewhere between northern Tasmania and a rural Victorian property after disembarking from the Spirit Of Tasmania in Melbourne on January 29, while on the return journey home.

Andrew Williams has spoken of his distress over the ponies' deaths. ( Supplied: Willo Polo )

Former captain of the Australian polo team and Willo Polo owner Andrew Williams was driving one of two trucks his club had used to supply horses for the event at Barnbougle, at Bridport in Tasmania's north-east, between January 20 and 24.

Williams said about an hour after leaving the ferry, he "knew something was wrong" due to the lack of movement from the back of the truck and upon stopping at a friend's property at Yarra Glen, he found 16 ponies "cold dead" and two "fighting to survive".

Seventy-eight days have passed since the deaths of the ponies on January 29, with almost nothing publicly known about how they died.

Pathology reports were released to Tasmania's Department of Primary Industries, Parks, Water and Environment (DPIPWE) months ago, but the department will not say when, or even if, it will ever release the findings.

The Tasmanian branch of the RSPCA requested information from the Tasmanian Government, but is also in the dark.

"We need to know what happened on that boat and the sooner the better, so we can make sure it doesn't happen again," RSPCA Tasmania chief executive and chief veterinarian Dr Andrew Byrne said.

"At the moment, there is a lot going around on social media that is not necessarily accurate, which is ill-advised.

Dr Byrne said he wanted information about the case released "as soon as possible".

"I believe this case will teach us a lot about looking after horses in transport," he said.

"We could learn a lot from it and the sooner we get that, the better."

One of two Willo Polo trucks parked on the vehicle deck of the Spirit Of Tasmania. ( Instagram: chelcroz )

Representatives of Tasmania's horse transport sector blasted authorities in February for not releasing information about the case, in the wake of a flood of inquiries from horse owners worried about their animals crossing Bass Strait.

Authorities said the ferry "appears to have complied with AMSA requirements relating to the carriage of livestock". ( ABC News: David Hudspeth )

The Spirit of Tasmania is a major sponsor of the Barnbougle Polo event, where the ponies had competed before their ill-fated return journey.

The ship's owner TT Line has so far chosen not to comment other than to point out an initial investigation by an Australian Maritime Safety Authority surveyor had found it "appears to have complied with AMSA requirements relating to the carriage of livestock".

Federal independent MP for Denison Andrew Wilkie said he was "staggered" nothing definitive had been forthcoming from investigators.

"In the absence of an effective investigation and it being released to the media, a cloud hangs over the Spirit and whether or not it's safe, over the department and whether or not it is effective and indeed over the integrity of the Government.

"I'm staggered that it's actually been about three months and still nothing has been revealed," Mr Wilkie said.

"Is it sitting on findings, and if so, why?"

After the backlash from the horse transport sector, including concerns about other Tasmania horse sales and events being compromised, DPIPWE moved to state it was "confident that there's not an ongoing risk for the transport of horses across Bass Strait".

A photo posted by the Barnbougle Polo club, announcing the "ponies had arrived". ( Supplied: Barnbougle Polo )

Mr Wilkie said the issue had "become so much more than the deaths of those ponies on the Spirit".

NSW polo identity Andrew Williams. ( Facebook: Willo Polo )

"This is about the effectiveness of the Department and whether or not it regulates things effectively, whether or not it has the competency to investigate when things go wrong. And indeed it goes to the Government," he said.

"It is a fundamental measure of a government's integrity that it be honest and open and transparent, and in this case the Government is looking increasingly secretive."

Inquiry needs to 'run its course'

Tasmanian Treasurer Peter Gutwein said the investigation should be allowed to run its course.

"Yes, I do think that they should have faith in TT Line," Mr Gutwein said.

"However, in terms of the current investigation, let's allow that to take its course.

"If there are matters that need to be investigated further or if charges need to be laid, let's not prejudice the outcome of that investigation."

Previous attempts by the ABC to contact Willo's Andrew Williams, his legal team and the organisers of the Barnbougle Polo event for comment remain unanswered.

Williams said after he found the ponies dead in his truck, he drove them to Wagga Wagga equine hospital, which is at the Faculty of Science at Charles Sturt University, New South Wales.

The hospital, which conducted autopsies on the ponies, has refused to release any information, including what happened to the two ponies which were found to have initially survived the Bass Strait crossing.

A truck used for carrying polo horses, owned by Willo Polo club. ( Facebook )

The multi-agency investigation into the ponies' deaths is being led by DPIPWE, and has also included the Victorian Department of Agriculture.

Andrew Williams has captained the Australian polo team and now offers coaching services. ( Supplied: Willo Polo )

Dr Byrne was previously working on the Australian mainland and said he "hadn't dealt with the Government in Tasmania before".

"I know that certain wheels move slowly ... it could well be that they are trying to be extremely thorough with this case before they say anything about it," Dr Byrne said.

Despite that, he said information should be released "so that we can advise other clients, other people that are moving animals around".

The RSPCA's national office said once the investigation was complete, it would "strongly urge the Government to make the report into the death of these ponies public to help ensure this does not occur again".

In its latest statement provided to the ABC, DPIPWE said investigation information was "necessarily confidential and cannot be made public at this stage".

"Additionally, it is not possible to offer an indication of time frames or progress during the investigation.

"The department will make information public if it is appropriate to do so, in accordance with confidentiality and legal requirements."

DPIPWE said in March it expected more laboratory results "soon", which "may or may not contribute to understanding a cause".

"At the conclusion of matters, whether it results in a legal prosecution or alternative actions, if information is identified that may assist the industry to enhance animal welfare outcomes, then this information is provided to industry stakeholders," it said in a statement to the ABC.