A man from Cospicua was yesterday morning helping the police in their investigation of Saturday's bomb blast that police believe was intended to kill a woman but ended up injuring two innocent people who mistook the bomb for a bag of rubbish.

The man had to be released in the afternoon after the 48-hour arrest period elapsed.

The explosion occurred at about 12.45 p.m. in Triq il-Madonna tal-Hniena, in Zejtun. Police sources yesterday outlined the sequence of events leading up to the blast.

At about 10.30 a.m., Tessie Grima, 60, was on the roof of her house when she saw a man placing a bag beside a car. The woman is reported to have shouted out to the man not to leave any rubbish in the street because it would not be collected until after the weekend.

But the man ignored her and drove off in his car, leaving the bag where he had put it. The woman was heard complaining that rubbish had been left lying in the street in spite of the fact that the village feast was being celebrated in Zejtun that weekend.

About two hours later she decided to remove the bag of "rubbish". However, she found it too heavy to carry on her own and asked a passer-by for help. Angela Bondin, 48, from Paola, obliged.

The two women lifted the bag and threw it into a garage under construction across the street. As the two women chatted in the middle of the road, the street was rocked by a powerful explosion from the bag, leaving Mrs Grima with 40 per cent burns and Mrs Bondin suffering from 15 per cent burns.

They were rushed to hospital and Mrs Grima was still in a critical condition yesterday.

Police sources said the bag contained explosive material, a detonator that was meant to have been operated by remote control and a motorcycle battery as well as several bullets which turned into shrapnel when the bomb went off.

They said the detonator mechanism had probably been jolted when the bomb was moved.

It could have been even worse for the two women. They happened to be shielded by a van when the explosion occurred and might otherwise have been killed or more seriously injured, the sources said.

The police suspect the bomb was intended for a woman from Cottonera who visits her mother in Zejtun and always parks her car in the same place at the same time.

The investigators believe the motive was revenge. It is understood that the person held by the police yesterday is facing a separate murder charge.