The Maldives government insisted on Sunday that its president had survived an assassination attempt on his boat even though the FBI found no evidence of a bomb blast.

In September, an explosion on President Abdulla Yameen Abdul Gayoom's speedboat slightly injured his wife, an aide and a bodyguard - although the president was unhurt. The couple were returning home following a trip to Saudi Arabia for the Haj.

Officials initially believed the incident was caused by a mechanical failure but later launched a murder investigation and last week arrested Vice President Ahmed Adeeb.

President Yameen rose to power in 2013 in a bitterly contested presidential election against the first democratically elected leader, Mohamed Nasheed. Earlier this year, Nasheed was arrested and given a 13-year jail term on terrorism charges, a sentence widely condemned by the international community.

The Maldives government asked the US, along with Saudi Arabia, Sri Lanka, India and Australia for help with the investigation into the blast. The FBI's report, released on Saturday, said there was no evidence that a bomb caused the explosion.

Vice President Ahmed Adeeb has denied any involvement in the explosion

Interior Minister Umar Naseer described the US domestic intelligence agency's account as "inconclusive," adding that Saudi Arabian and Sri Lankan investigators had confirmed the likelihood of a bomb.

"The FBI report only said there wasn't conclusive evidence found from the scene to suggest that an explosive device had been used to trigger the blast," Naseer told reporters in the capital Male. The US team had taken 10 samples, none of which had shown traces of an explosive, he said.

"Traces of high-grade explosives were found from one of the samples (taken by the Saudi forensic team). This finding is also backed by the team from Sri Lanka," Naseer added.

FBI spokesman Josh Campbell said in a statement to Reuters: "Based on the FBI's analysis - which included forensic analysis of the scene, analysis of the items recovered from the scene, and chemical testing - there is no conclusive evidence to attribute the explosion on the boat to an IED."

A major shake-up of the president's security was ordered after the explosion. As well as the arrest of Vice President Ahmed Adeeb "on suspicion of involvement in the boat blast," several of his associates were detained. Officials say a further eight suspects are believed to be hiding in neighboring countries.

Maldives police arrested seven people on Saturday after finding weapons hidden on the seabed.

mm/ng (AP, AFP, Reuters)