A senior PSNI officer has said that the two pipe bombs which exploded outside the homes of two Romanian families in the Waterside area of Londonderry last Saturday morning were both packed with nails.
The pipe bombs exploded within minutes of one another outside the front doors of the houses at Lincoln Court and Lapwing Way.
No-one was injured in the no warning explosions which the police say they are treating as hate crimes.
Chief Supt Jon Burrows said that two men, one aged 40 and the other aged 32, were arrested on Monday in relation to the attacks.
He explained: "Both pipe bombs contained nails and exploded outside the homes of two Romanian families. My officers are working to bring those responsible to justice and to support and comfort the families.
"Pipe bombs packed with nails are, as we know all too well in this city, potentially lethal weapons which can cause very serious injuries.
"I appeal to members of the community not to have any misplaced sense of loyalty to those who carried out these attacks. Putting nails into pipe bombs is a sinister development and we are treating this as a hate crime. Nails are put there for one reason only and that is to inflict serious injury. Only two families were attacked and they are both Romanian.
"The very small minority of people who do this sort of thing do not speak on behalf of the vast majority of the people in this city who are pluralist and kind."
The two men who were arrested are being questioned at Antrim Serious Crime Suite.