Bulgarian police have arrested four suspects following the deadly bomb blast in Razlog on September 1 which left a mother and a child dead and another child in critical condition, in the Sofia Pirogov hospital.

According to the deputy Prime Minister and Interior Minister Tsvetan Tsvetanov, quoted by the Focus News agency, "there were several reasons to believe that the suspects were involved in the case".

Businessman Yavor Mandradjiev, whose wife and child were killed in the blast,  was questioned by the police late on Tuesday.

Meanwhile, Tsvetanov told the media that he believes the attack was in retribution for other criminal activity.

"Of course, it is obvious that such assault in such brutal fashion is over criminal activity," he said, quoted by Focus news.

The bomb that killed two and severely injured a third person went off at about 8am as Mandradjiev's wife attempted to open her garage door. The victims were identified as the wife and child of 37-year-old Yavor Mandradjiev. Meanwhile, his second child, a nine-year-old, is fighting for his live in Pirogov hospital.

Earlier on Tuesday, Razlog deputy mayor Ivan Gyurov said that the man responsible for the blast is a well known criminal with a longstanding criminal record involving racketeering, fraud and smuggling of goods.

However, Gyurov declined to release further information, saying that "rumours about what this person did and how he came across so much money are rife, but whatever I say at this stage will be merely gossiping",  Dnevnik daily quoted him as saying.