LONDON (AP) — British police say they are "aware" of a claim of responsibility by Irish dissidents with regard to the sending of pipe bombs last week.

The Metropolitan Police said Tuesday that a media outlet in Northern Ireland received a claim of responsibility Monday using a recognized code word.

The group making the claim said five devices were sent, but police have so far only found four.

"The claim was allegedly made on behalf of the 'IRA,'" police said, referring to the Irish Republican Army. The IRA has been in a cease-fire for years but dissident groups are still active.

Police say they were already investigating possible dissident links to the packages, which did not cause any injuries.

The statement says counter-terrorism police are keeping an "open mind."