London ? British police Monday identified two of four men believed responsible for last week’s botched transit bombings and said an explosive found in a park was like those used in the attempted attacks, raising fears a fifth bomber was on the loose.

London’s police chief said the force was “racing against time” to find the bombers, who fled three subway trains and a bus when their devices failed to fully detonate. Those bombs and the one found abandoned Saturday all were made using clear plastic food-storage containers put into dark-colored bags or backpacks.

At a televised press conference, Peter Clarke, head of the Metropolitan Police anti-terrorist squad, held up one of the white-lidded, 1.65-gallon containers – called a Delta 6250 – and urged any shopkeeper who had sold five or more of them to contact police.

Earlier, Prime Minister Tony Blair apologized for the killing of a Brazilian electrician mistaken for a terrorist as officials confirmed that undercover police shot him eight times – one in the shoulder, seven in the head. Blair also urged Britons to come forth with information on the fugitive bombers.

Police identified two of the suspects as Yasin Hassan Omar, 24, and Muktar Said Ibrahim, 27, also known as Muktar Mohammed Said, but did not give their nationalities.

Authorities also released new closed-circuit images of the four suspects and gave details of their movements, recounting how one bolted from a subway station pursued by passengers, while another jumped through a subway window and fled down the tracks.

On Sunday, police destroyed a package found by a passerby in bushes in a west London park not far from the scene of the attempted bombing at Shepherd’s Bush station. Clarke said forensic examination showed “clear similarities” between the device and the four bombs found Thursday.