The official Bahrain News Agency quoted the public security chief, Maj. Gen. Tariq al-Hassan, announcing the arrests Wednesday. He did not provide further details.
Police say the remotely detonated blast early Tuesday in Sitra, south of the capital Manama, targeted a bus carrying policemen near a primary school for girls.
Two police officers were killed and six were wounded. Bahrain is a Sunni-ruled kingdom that is home to the US Navy's 5th Fleet.
It has faced years of clashes between anti-government activists and police following widespread 2011 protests that were led by its Shiite majority calling for greater political rights. Several small bombs have targeted police in recent years.