The intensity and modus operandi of the Mumbai blasts have led to suspicion that terrorist outfits from across the border have caused the explosions with the help of local elements, the Rajya Sabha was told on Tuesday.

"Given the past experience and the magnitude, scale, intensity and modus operandi of the Mumbai bomb blasts, we suspect that terrorist outfits from across the border have caused these blasts with the help of local elements," Sriprakash Jaiswal, Minister of State for Home said in a statement.

He said preliminary investigations have revealed that the explosives used were a mixture of RDX, ammonium nitrate and fuel oil.

Seven cases have been registered and four arrests made so far, he said, adding the government remains committed to apprehend and punish all those responsible for these 'barbaric acts of terror' in Mumbai.