Investigators in the bombing of the U.S. Embassy in Tanzania said Saturday they had made "extraordinary discoveries," having determined what the bomb was made of and who carried it to the embassy.

Police also had two suspects and three informants in custody, said Rajabi Adadi, Tanzania's director of criminal investigation."Investigators have made extraordinary discoveries," said Kenneth Piernick, head of the FBI investigators in Tanzania. "They are now well aware of the composition of the bomb and are also well aware how the device was delivered and who delivered it."

He refused to elaborate.

Adadi said one of the suspects arrested is Tanzanian and the other is a foreigner. He would not identify the foreigner or his nationality but did not deny media reports that the suspect was Sudanese.

Twin bombings at U.S. Embassies in Dar es Salaam, Tanzania, and the Kenyan capital Nairobi on Aug. 7 killed 258 people and injured more than 5,400. Of those killed, 11 were in Tanzania.

"Police have some leads regarding the event," Adadi said. "They know who took the device to the embassy, and they also know some of the people responsible for the event and others whose roles have not yet been proven."

He said the three informants had all participated in the preparations for the bombing, mostly unwittingly, and were now cooperating with the investigation.

Media reports in Tanzania have said the ingredients for the bombs had originated in the Middle East and were transferred by sea via the Comoros Islands to Tanzania. Similar reports in Nairobi said components were also transported from Tanzania to Nairobi by road.

On Wednesday, police in the Comoros island archipelago off Tanzania raided two homes and searched for a suspect in the bombings identified as Abdallah Mohammed Fadhul, a Comorian Muslim who had lived with his wife in Sudan until shortly after the embassy bombings.

Two key suspects in the Kenya bombing, in which 10 Americans were killed, have been handed over to the United States for trial.