Investigators suspect a known criminal gang specialised in high-stake robberies is behind the attempted bank heist using a tunnel.

The police received a tip-off months ago but initially did not know which bank was being targeted. Eventually, investigators located the garage near the Swieqi HSBC branch and mounted a surveillance operation lasting weeks but there was no sign of the criminals. It was then decided to raid the garage on grounds of safety because of the possibility of the tunnel collapsing if it flooded with winter rain.

Police Inspector Sandro Camilleri told Times of Malta on Monday that the police could not have waited for the robbers to continue digging the tunnel to nab them in the act as such action could constitute a form of entrapment.

But this opinion was contradicted yesterday by Assistant Police Commissioner Pierre Calleja, head of the Criminal Investigation Department.

He insisted that the law gave investigators the faculty to stake out the activity and even perform an arrest as the thieves made their way into the vault.

There could not be entrapment without having an agent provocateur and, in this case, it was very clear that the police had not solicited the perpetrators to dig the tunnel.