The health authorities are investigating the unexpected death of a young man who took the swine flu vaccine five days earlier, although initial results indicate just a "coincidental" relation between the two.

Clayton Cachia, 23, died on Wednesday evening at Mater Dei Hospital after he was taken ill from work.

Described by his distraught parents, Joseph and Pauline, as perfectly healthy, Mr Cachia was to be engaged to his girlfriend Ebony in two months' time.

The health authorities confirmed that an autopsy was held yesterday and medical tests were ongoing to determine whether the untimely death was related to the vaccine.

"Since the person was injected with the A(H1N1) influenza vaccine five days ago, the case is being followed very closely by the health authorities. From the information collected so far the relation between his death and the vaccine could possibly be coincidental," a spokesman said.

Mr Cachia's sudden death came as a complete surprise to his parents and only sister, Romina.

"He was a healthy six-foot-four boy," his mother said, adding he took the swine flu vaccine on Saturday after being advised to do so at his work place. Mr Cachia had only just started working as a medical representative with a pharmaceutical company two months earlier.

"I do not know whether his death is linked to the vaccine. Doctors said it was not but I don't know. I don't know. I have not taken the vaccine and will not take it myself," his mother added.

"I am going to die," his grieving father said, pointing out that doctors had taken all the necessary tests and sent them abroad.

"They told us his heart swelled. He took the injection on Saturday... I don't know if it was a reaction to the vaccine," he said.

Mr Cachia was an "exemplary" child who, according to his mother, "brightened up the street" with his charm.

An avid Manchester United supporter, Mr Cachia had left home at 5 a.m. after kissing his mother goodbye. He collapsed at work a few hours later.