The FBI says there is no evidence to confirm that last month's explosion aboard the Maldivian president's boat was caused by a bomb, an allegation made by the government that has led to the arrest of the country's vice president.

The government has accused the vice president of the Indian Ocean archipelago for plotting to assassinate President Yameen Abdul Gayoom.

The explosion took place Sept. 28 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.

Police have arrested Vice President Ahmed Adeeb and three soldiers.

The FBI said in a statement Saturday that the debris it was asked to investigate turned out to be boat parts and not bomb remnants.

"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," the statement said.