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

President Abdulla Yameen was unharmed in an explosion on his speedboat on September 28 that slightly injured his wife and was described by authorities as an attempt on the leader's life.

Police arrested Vice President Ahmed Adeeb almost a month later for treason, fuelling fears of fresh political turmoil in the honeymoon islands after a series of sackings of senior government officials.

Home Minister Umar Naseer said he had received a report from the Federal Bureau of Investigation (FBI), which found no evidence that a bomb caused the explosion.

But Naseer described the US agency's report 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, but none of which had shown traces of an explosive."

"The Saudi forensic team had taken a total of six samples for analysis. Traces of high-grade explosives were found from one of the samples. This finding is also backed by the team from Sri Lanka," he said without releasing their findings.

The FBI found that debris from the blast, at first considered possible remnants of a bomb, were in fact parts of the boat, The Wall Street Journal reported on Saturday.

The Maldives asked the US, Saudi Arabia, Sri Lanka, India and Australia for help with the blast investigation.

Since the explosion, the president has ordered a major shake-up of his security and sacked several of his ministers, while several of Adeeb's associates have also been arrested.(AFP)