Updated 1pm

An explosives team was called to the Labour Party headquarters at around 8am on Thursday after security personnel spotted "a small device" on the ground outside the Ħamrun building.

Neighbours meanwhile reported they heard "a small explosion" in a dustbin outside the headquarters at around 2am.

Nobody was injured but the people inside the building were evacuated on Thursday morning 

A large police contingent turned up on site and the road was closed while investigations were ongoing.

By 1pm people were given the all clear to re-enter the building.

Photo: Matthew Mirabelli

PL president Ramona Attard said a small explosion was heard in the early hours on Thursday and the place was evacuated: "We are very calm and letting the police and the AFM bomb squad do their work".

Prime Minister Robert Abela meanwhile said on Facebook the small explosion was heard at night. He urged for calm.

Police officers and sniffer dogs making sure the area outside the PN HQ is safe. Photo: Matthew Mirabelli

Bernard Grech and the Nationalist Party expressed solidarity with the PL in a statement.

Grech offered his support to Abela, deploring the act and saying he hoped that those responsible were caught.

The party also asked for police to comb the surrounding area of the PN headquarters because of the "risk of similar action".

It later thanked the armed forces and police for their work.

Magistrate Ian Farrugia opened an inquiry into the explosion.