Interior Ministry spokesman Salah Salem described the material as "highly explosive" and said it was undergoing further analysis. Authorities gave no details on possible suspects.

Salem said the blast ripped away one of wheels from the minibus and shattered its windows in a public parking lot about 50 meters from the British Embassy.

"There were no casualties or damage to the embassy. We cannot identify yet the cause or the responsibility," a British Embassy official said. "We are working with the Interior Ministry and we have requested a temporary increase in security."

Meanwhile, a military court sentenced Sunday a bodybuilder and two sportsmen to one year in prison for taking part in protests that the government quelled earlier this year, a lawyer said.

The three are bodybuilder Tareq Al-Fursani, a gold medallist in several Asian championships; Ali Said, a goalkeeper in the national soccer team; and Mohammed Hassan Al-Dirazi, a member of the national basketball team, said lawyer Mohsen Al-Alawi, who was in court when the verdicts were read Sunday.

The men, who are not in detention and can appeal their convictions, were tried in a military court because they are employees of the Bahrain Defense Forces. They were found guilty of illegal congregation, inciting hatred for the system, and not obeying orders regarding involvement in politics.