Police in Lurgan believe another explosive device could have been planted in the area where a bomb attack took place at the weekend.
A senior officer yesterday reminded the public to be vigilant following the bomb attack on Saturday.
Dissident republicans were blamed for the explosion near Victoria Street.
Officers were called to the scene after a phone call to the Samaritans claiming a device aimed at a police patrol during the early hours had failed to explode.
Homes were evacuated and a hoax device, which was not capable of detonating, was discovered.
But during a follow-up search a bomb designed to "take out officers on foot" exploded.
Superintendent Davy Moore said yesterday that the PSNI investigation into the weekend security alert continues.
"I would like to remind the public to remain cautious in the area of Lake Street and Victoria Road," he said. "Please be vigilant and if you notice anything of a suspicious nature please contact us immediately on 101 or 999 in an emergency."