There is no evidence that last month's explosion aboard the Maldivian president's boat was caused by a bomb, the FBI said, contracting government allegations that have led to the arrest of the country's vice president and deepened the turmoil in the Indian Ocean archipelago.

The Maldives' government has accused Vice president Ahmed Adeeb of plotting to assassinate President Ymeen Abdul Gayoom on Sept. 28. He escaped unhurt because he wasn't sitting in his usual seat on the boat, the government said. His wife, an aide and a bodyguard were injured.

The FBI said in a statement that the "submitted specimens were determined to be components from the boat and not the components of an improvised explosive device."

"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," it added.

The Maldives sought assistance from the FBI, as well as investigators from Sri Lanka, India, Australia and Saudi Arabia.

Home Minister Umar Nazeer has said previously that the investigation by Sri Lankan experts found that the explosion was caused by a device that was small and designed not to kill everyone on board. According to Nazeer, it was meant to kill or incapacitate the president. Nazeer did not say anything about the type of the explosive device or how it was detonated. He did not answer phone calls seeking comment on Saturday and Sunday.

He seemed to have contradicted the FBI statement, writing on his Twitter account that "FBI examiners did not conclude that there was no IED in the blast.ie: they did not rule out an IED" on the boat.

Investigators from India, Australia and Saudi Arabia have not yet released the results of their probes.

The explosion took place as Gayoom and his wife were returning to the capital from the airport, which is on a separate island. Gayoom escaped unhurt, but his wife, an aide and a bodyguard were injured in the blast.

Adeeb's lawyer on Saturday called the allegations against his client untrue.

Authorities carried out raids on the homes and businesses of Adeeb's associates, but have refused to give any details about what may have been found. Gayoom has also fired his defense minister and the police commissioner after the blast.

The blast and the arrests deepened political unrest and power struggles in the Maldives since it held its first elections in 2008, after 30 years of autocracy under Gayoom's half-brother.

Gayoom won the presidency in 2013, after disputed elections against a predecessor who was forced to resign three years earlier amid public protests. Former President Mohamed Nasheed is now serving 13 years behind bars on a conviction delivered in a rushed trial widely criticized as unfair.