Police are liaising with army bomb disposal experts to decide when to send in officers to investigate a road-side bomb near Belleeks in south Armagh.
Saturday's blast destroyed part of the Carrickrovaddy Road and a stone bridge.
A senior officer said the explosion showed the threat posed by dissident republicans to police in the area is "substantial".
The device blew a crater in the road, but no-one was injured.
Police are working "with extreme caution" in follow-up searches, amid fears of hidden bombs. Surrounding roads will be closed for some time.
"This was a blatant and callous attempt to kill and injure my officers," Superintendent Pauline Shields said.
"We believe there is currently no real risk to members of the public; this is a small, isolated country road. But there is a real risk to my officers.
"That is why we have to assess the situation and take the right action to keep both the community and my officers safe.
"However, we are doing everything in our power to keep them safe and to investigate the incident."
She said "indications at this stage would suggest the involvement of dissident republicans".
Northern Ireland Justice Minister David Ford said the explosion was "designed to kill, maim and frighten".
"The days of the bomb and the bullet are in the past, and thankfully no-one was injured in this blast which was an attack on the entire community," he said.
Sinn Fein MP for Newry and Armagh, Conor Murphy, said it had created a "huge inconvenience" for people in the area.
"The sole outcome of this attack is that the Creamery Bridge has been destroyed and the road has been closed," he said.
"One would also have to take into consideration the fact that this bomb could have seriously injured local people travelling on this road, a fact which the perpetrators seem to have ignored."
DUP assembly member William Irwin said: "Over recent months, dissident republicans have been using primary incidents to lure police into the area so that a secondary device can target police officers trying to protect our community.
"This was clearly another attempt to kill or injure police officers as part of a larger terrorist operation."
Ulster Unionist assembly member Danny Kennedy said he had "no doubt it was an attempt to raise tensions in the area before the Twelfth of July".
SDLP assembly member Dominic Bradley added: "Whatever the reason for it and whoever's responsible for it, it's wrong and shouldn't be happening."