Russian officials have invited a French ocean explorer to offer advice on how to safely release nearly 100 illegally captured whales, voicing hope that the animals could be let into the wild during summer.

Jean-Michel Cousteau of the Ocean Futures Society arrived on Friday in Russia’s Far East on a mission to inspect the mammals and help create conditions for them to be released.

Mr Cousteau, son of famous oceanographer Jacques Cousteau, has voiced concern about the animals’ condition and offered his help to the Russian government.

The whales’ condition has drawn international concern, and Vladimir Putin has ordered authorities to investigate the case and release the animals.

Russian prosecutors have brought criminal charges against four companies keeping the whales.

Tragic photos show beached whales Show all 15 1 /15 Tragic photos show beached whales Tragic photos show beached whales A dead sperm whale lies on Hunstanton beach in Norfolk on 5 February 2016 AFP/Getty Tragic photos show beached whales Volunteers pour buckets of water over the 80 remaining live pilot whales found stranded on remote Ocean Beach on New Zealand's southern-most Stewart island, 8 January 2003 AFP/Getty Tragic photos show beached whales Contractors clear away the body of one of the dead 48ft sperm whales that were washed-up on a beach near Gibraltar Point in Skegness, Lincolnshire in 2016 PA Tragic photos show beached whales People pass by a beached whale at the Pointe de la Torche, near Brest in France on 29 November 2011 AFP/Getty Tragic photos show beached whales A woman touches the tail of a large whale carcass on Wattamola Beach at the Royal National Park in Sydney on 25 September 2018 AFP/Getty Tragic photos show beached whales Beached humpback whale in California, 2015 AFP/Getty Tragic photos show beached whales Dead long fin pilot whales at Hamelin Bay on Australia's west coast on 23 March 2009 AFP/Getty Tragic photos show beached whales A 36ft sperm whale lies dead on the beach at Sutton Bridge, in The Wash, off the Lincolnshire coast, where it became stranded in 2004 PA Tragic photos show beached whales A female fin whale opens its mouth as it lies stranded and alive on the beach at Carlyon Bay, Cornwall on 13 August 2012 Getty Tragic photos show beached whales The lower jaw of a dead sperm whale that stranded itself on a beach in Hunstanton, Norfolk on 5 February 2016 Getty Tragic photos show beached whales One of the five sperm whales that were found washed ashore on beaches near Skegness, Lincolnshire over the weekend on 25 January 2016 Getty Tragic photos show beached whales Employees at work to skin the remains of a beached 60ft whale on 25 January 2013 AFP/Getty Tragic photos show beached whales Two long-finned pilot whales are stranded on a beach in the northern French city of Calais on 2 November 2015 AFP/Getty Tragic photos show beached whales A sperm whale lies dead after becoming stranded on a beach in Hunstanton, Norfolk on 5 February 2016 Getty Tragic photos show beached whales Crowds gather as a sperm whale lies dead after becoming stranded on a beach in Hunstanton, Norfolk on 5 February 2016 Getty

Whales are worth a fortune on the black market, and local environmental activists suspected that they were captured for sale to amusements parks in China.

Russian law only allows for the capture of whales for “scientific” purposes.

Regional governor Oleg Kozhemyako met with Mr Cousteau in Vladivostok, voicing hope that his experience will help “get a full picture on how to allow the animals to readapt to living in the wild.”

Before flying to the Far East, Mr Cousteau met with Russian natural resources minister Dmitry Kobylkin in Moscow on Thursday.

Mr Kobylkin said summer offers the most favourable conditions for releasing 97 belugas and orcas.

“We couldn’t release the animals in the winter, it would have simply killed them,” Mr Kobylkin said. “We can and must do this work in the coming summer.”

He emphasised that Russia would like to rely on international expertise to ensure the safe release of the mammals.

“We want to do it as openly as possible,” Mr Kobylkin added.

Russian scientists estimate that the rehabilitation effort will cost about 300 million rubles (about £3.5m).

Activists first raised the alarm late last autumn when 101 belugas and orcas were captured and placed in a marine containment facility that environmentalists have dubbed a “whale prison” near the far eastern port of Nakhodka.

Local prosecutors have said that several of the mammals have escaped, but environmentalists said four animals likely died because of cramped conditions and low temperatures.