Investigators do not have enough evidence to make their case against two more men they suspect of involvement in the attempted robbery of HSBC headquarters two weeks ago, which ended in a shootout with the police.

The two men arraigned so far in connection with the case are said by sources not to be cooperating witht he police in any way. Investigators are therefore having to rely on the forensic examination of trace evidence found at the scene and at several locations believed to have been used by the suspects.

The evidence points to two well-known criminals but the sources said the police were being especially cautious because they have been chasing these individuals for years without success and anything short of a watertight case could waste a golden opportunity to finally put them behind bars.

The men top the suspect lists of past heists, including hold-ups on the HSBC Balzan branch in which the robbers made away with €1 million and on the Casino di Venezia, which was cleaned out of some €500,000 in cash, jewellery and cheques.

Two suspects, Darren Debono, 33, and Vincent Muscat, 48, were charged last week and remanded in custody.

Besides attempted robbery, they were also charged with trying to murder constables Kenneth Ciangura and Kurt Gauci, two members of the Mobile Squad who were involved in the shootout, as well as with holding Constable Dominic Bugeja, a member of the Special Assignments Group who was guarding the entrance to the Qormi bank, and taking his issue pistol.

The suspects are said to have escaped in a getaway car after being surprised by the police who showed up outside the bank and exchanged fire with them.

Two days later, however, Mr Debono was forced to seek medical help for bullet wounds to the jaw and leg.

He was denied help at a private clinic and whisked off to Mater Dei Hospital, where he was treated under the watchful eye of the police.