Five workers were injured when part of a construction site in Corradino Industrial Estate collapsed, while another man is still missing, the police said.

The accident happened at around 9.30am, with footage that emerged on the social media later showing that a corner of the building seemed to give way, pulling down the whole edifice which ended in a mound of debris.

Home Minister Byron Camilleri said the missing worker is a 20-year-old man, for whom a search is taking place. It is understood that the man who is still missing entered the building a few minutes before the collapse.

Addressing the media, Camilleri said that the CPD likely knows the location of the trapped person. Drones and police dogs are helping the CPD and police in the search operation.

Camilleri added that there is a possibility that there could be a controlled collapse of part of the building that has remained standing. This was being said upfront so as not to create unnecessary alarm, he said.

CPD director Peter Paul Coleiro said that through equipment used, the CPD has narrowed down the location of the person who is trapped to 10 metres. The steps that will be taken next is to remove, as delicately as possible, the rubble that is on top so as to be able to reach out to him.

He said some walls will need to be brought down with the possibility that other parts of the building will collapse.

Coleiro said that the intention is to push the rubble away from the location where it is thought that the trapped man is.

Camilleri added that from information gathered, including through the use of security cameras, there were six people on site at the time of the accident.

The five workers who were pulled out of the rubble were taken to hospital. 

Health Minister Chris Fearne initially tweeted that two of them were in intensive care, but the police later said that three were in ITU. The other two suffered grievous injuries. One of them, the police said, is a Maltese man aged 42 who lives in St Paul's Bay.

Three of the other injured workers are from Albania, and the other one is from Bosnia. 

At around 12.30, a man turned up on the site asking the police whether they had found the missing person. He was held back by officers from approaching the site of the collapse.

The rescuers are hampered by the rubble as well as the possibility that other parts of the building could collapse, a police spokesman said.

Around 30 members of the Civil Protection Department are taking part in the rescue operation.

In a post on Facebook, Home Affairs Minister Byron Camilleri urged people to avoid the area so as not to hinder the authorities, adding that four workers had been rescued.

In a second post later, he said that a fifth person had been freed by the rescuers.

Magistrate Marseanne Farrugia is leading an inquiry.

Police and ambulances are on site.