The incident, which took place on Friday shortly after 7am on Kennedar Drive in Govan, left two people injured.
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Police said the explosion was a result of “a deliberate act within the flat”, which was significantly damaged.
Twenty-three people in the block of flats were evacuated as a precaution while emergency services dealt with the incident but were later allowed to return to their homes.
Two of the flat’s occupants, a 26-year-old man and a 30-year-old woman, were taken to hospital for treatment following the blast.
The man sustained burns as a result of the explosion and remains in a critical condition, whilst the woman was discharged on Friday having been treated for minor injuries.
Officers are continuing with their enquiries into the incident.