A child's car seat could be a vital clue for detectives seeking the gang which murdered Detective Adrian Donohoe a month ago near the border.

The 41-year-old father of two was shot dead during a robbery at the Lordship Credit Union, outside Dundalk, in a 4,000 robbery on January 25.

Investigators issued an appeal on Tuesday for help in tracking down the seat, which had been fitted to the VW Passat car used by the five-strong gang in their getaway after the murder.

The green-colored seat, suitable for an eight or nine year old, was not in the car when it was found burnt out in south Armagh.  Gardai are now trying to establish if it was dumped somewhere or else offered for sale.

The Passat was stolen from outside a house in Clogherhead, Co. Louth, on January 22/23, and Gardai are anxious to hear from anyone who might have spotted a similar model of car seat or was offered one for sale since then.

Officers also asked for help in tracing the history of a precision mallet-type hammer, which was used by the gang to smash the windows of the cars used by credit union officials at the scene of the robbery.

Gardai confirmed there were five members of the gang involved in the raid, and pointed out that only one fired the fatal shot which killed Donohoe.

One officer said at a press conference on Tuesday, “We don’t believe the others were aware that a Garda was to be shot and we are anxious that they contact us.”

A reward for information leading to capture and conviction of the killer has been doubled to 100,000, with the Crimestoppers organization adding 50,000 to the 50,000 already offered by the Irish League of Credit unions.

Gardai believe they know the members of the gang and are steadily gathering sufficient evidence with the help of the Police Service of Northern Ireland to bring them to trial.

The Sunday World has reported that they are believed to be a girl aged 16 who drove the getaway car, two of her brothers in their 20s, and two other men in their 20s. All live in South Armagh and, according to the Sunday World, have links to well-known GAA club Crossmaglen Rangers.

Police are still on the hunt for the murderers of Irish Detective Adrian DonohoeGoogle Images