A section of the Strand Road in Londonderry remains closed after Tuesday's car bomb.
A taxi was hijacked and packed with 200lbs of homemade explosives. The driver was ordered at gunpoint to leave the car at Strand Road police station.
No-one was injured in the explosion which has been blamed on dissident republicans.
The cordon point at Strand Road/Clarendon Street has been moved to the Strand Road/Asylum Road junction.
Boating Club Lane has now been reopened up to the junction of Strand Road.
The other point at Strand Road/Lawrence Hill remains in place.
Police said the roads around the police station were likely to remained closed until Thursday.
No-one was injured in the attack which happened at 0320 BST on Tuesday but several businesses were badly damaged in the blast.
Divisional Commander Steve Martin said it was fortunate no-one was killed because the device went off more than 20 minutes before a warning said it would.
He also revealed that a policeman risked his own life when he walked past the bomb twice to bring to safety staff at a nearby fast food shop.
The first and deputy first ministers condemned the attack.
Peter Robinson said he was thankful there was no loss of life.
"Using a taxi driver to deliver the device shows the cowardice of those behind the attack and my sympathies are with him and all those targeted," he said.
Martin McGuinness said those who planned the attack were an "embarrassment" to the people of Derry.
"If they think they will destroy the political institutions the people of Ireland voted for, if they think they're going to destroy the working relationship I have with Peter Robinson, if they think they will undermine the peace process they are living in cloud cuckoo land," he said.
In May, a mortar bomb was fired at the same police station. It struck a wall but failed to explode.
The attack comes just weeks after Derry was picked to be UK City of Culture in 2013.