The officer sustained serious leg injuries in the explosion
Four men arrested over the attempted murder of a police officer in County Tyrone last week have been released without charge.
The officer suffered leg injuries when a booby-trap bomb on his car exploded at Drumnaby Road in Spamount village, outside Castlederg, last Monday.
The four men had been questioned for several days.
A man and a woman also arrested over the attack were released pending further inquiries.
The scene of the attack - which has been blamed on dissident republicans - was revisited by police on Monday night.
Detective Inspector Ian Magee said he hoped the exercise might help jog the memories of people in the area.
"Fortunately, the injured officer is making a good recovery. He has undergone operations, including skin grafts, and is in good spirits," he said.
"The officer's car was not used between 6pm on Saturday May 10 and 9pm on Monday May 12.
"We believe that the device was placed under it sometime in this period and I am asking, did anyone see strangers, strange cars or suspicious activity in the area in this period?"
In November, the Real IRA shot two officers in Londonderry and Dungannon, and in February police mounted a huge security operation across Northern Ireland because of fears that dissidents were planning another shooting or bombing.