Spanish police are investigating the deaths of around 70 migrants trying to reach the Canary Islands following horror claims some were murdered and their bodies thrown into the Atlantic Ocean. Survivors claimed an unspecified number of alleged victims were shot dead after the overloaded boat they were on suffered engine problems.

Unconfirmed reports first published yesterday by Spanish news website Okdiario claimed between 20 and 30 migrants are being investigated on suspicion of carrying out the “executions”. The migrants, now in refugee centres, reportedly accused others on board of stealing water and then witchcraft as supplies dwindled. Detectives are “close to making the first arrests” over the alleged incidents while the boat was adrift for more than a week before its rescue by Spanish coastguards, reports added.

Police have yet to comment on the website’s report or another overnight by respected Spanish news agency EFE saying they had witness statements claiming “some murders” were committed on the boat.

Survivors are also said to have told investigators that several migrants died of thirst and hunger and others threw themselves overboard after suffering delirium caused by dehydration.

It was not clear this morning if any women or children are among the alleged victims.

Spanish coastguards rescued around 250 people on board the stricken boat west of the city of Dakhla in the disputed Western Sahara territory, 265 miles from the Canaries, following an August 24 alert from a passing merchant vessel.

Survivors are understood to have told officials after they were brought ashore at Arguineguin on Gran Canaria’s southern coast on August 25 around 320 people started the journey before they ran into problems at sea.

In June Spanish police confirmed they had launched an investigation after the bodies of five migrants were found in the sea off the Balearic Islands with their hands and feet bound.

Initial speculation centred on the possibility they could have been murdered and thrown overboard.

The families of the men who died, all Somalians, later revealed they were shackled in a death ritual after they perished from starvation as they tried to reach Europe.

They had been on a boat that was rescued on May 8 by Spanish coastguards 62 miles from Alicante, with 16 male survivors suffering dehydration and other health problems and a dead man on board.

The vessel left Algeria a fortnight earlier before it was left adrift following engine problems.

During their trip they ended up having to eat just one date a day and drink their own urine, with the men whose bodies were recovered from the Mediterranean said to have fatally opted to drink sea water to try to survive.

Red Cross chiefs said after their rescue: “One of the people rescued had eaten toothpaste because it was the only thing he had. He didn’t want to let go of the tube when he reached dry land.”