GRAN CANARIA/RABAT (Reuters) - Spain said on Friday it was probing reports of casualties among a group of migrants trying to reach the Canary Islands from Africa, after a charity cited survivors as saying Moroccan soldiers opened fire killing at least one of them.

The Moroccan authorities did not immediately respond to emailed and telephoned requests for comment on the allegation that its forces shot at the group of more than 40 migrants as they sought to depart on a dinghy early on Tuesday morning.

Reuters could not independently verify the report.

"We are investigating," a Spanish police source told Reuters, referring to reports of injuries.

One account of the incident citing unidentified survivors for the death of a migrant was posted on Twitter by the Walking Borders charity that documents migrants missing at sea.

Following the incident, the group managed to depart and were eventually recovered 12 miles south of Gran Canaria at 9 p.m. on Thursday night in a rescue involving Spanish helicopters and patrol boats, officials in the Canary Islands said.

The migrants told rescuers they had set sail from the small town of Boujdour in Moroccan-controlled Western Sahara, 200 nautical miles south of the Canary Islands, officials said.

A spokesperson for the Spanish government in the Canary Islands said it had no record of gunshot injuries among the arriving migrants -- 32 men, nine women and a girl -- but that three of them required medical care including a pregnant woman, another "unwell" person and a third with a "leg trauma".

But a Spanish police source later said one of the three migrants being treated for injuries in the Canary islands had bullet exit and injury wounds, and police were gathering evidence for an investigation.

Helena Maleno, head of Walking Borders, said survivors of the incident who remained in Morocco had told her by telephone that soldiers on an anti-migration patrol fired up to four rounds of gunfire at the boat as it embarked, hitting a young Malian man in the neck and killing him.

Txema Santana, an adviser on migration to the Canary Islands government, told Reuters the migrants had told rescuers that two people had been killed by shots fired by what they described as an "anti-migration checkpoint" before leaving Morocco.

Jose Antonio Rodriguez Verona, head of the Red Cross emergency team on the Canary Islands, said what exactly had happened remained unclear and the migrants who made it to the Canary islands did not identify who had opened fire.

"The migrants told us that there were two people who had died on the crossing and their bodies had been thrown overboard," he told Reuters.

Injuries to migrants are frequently caused by trafficking gangs following disputes, according to rights groups and migrants speaking previously to Reuters. However Moroccan rights groups including the CNDH state human rights council have also warned of the growing use of force by the Moroccan authorities in the control of migrants from Africa towards Europe.

Last year, at least 23 people were killed and scores left injured or missing in a mass border crossing attempt between Morocco and Spain's North African enclave of Melilla last year.

(Reporting by Borja Suarez, Corina Pons, David Latona, Inti Landauro, Joan Faus and Belen Carreno; Additional reporting by Ahmed El Jehtimi; Writing by Aislinn Laing; Editing by William Maclean)