Authorities in Gloucester County say the controlled burn of fuel at the site of a building explosion could take several more days to complete.

The explosion at Savita Naturals on Heron Drive in Logan Township Wednesday afternoon left four employees critically injured. A fifth person from a nearby business was also taken to the hospital for an undisclosed medical emergency. Three other people went to the hospital on their own to be treated for other various injuries.

Officials say that although air quality monitoring at the site continues, no hazardous materials have been detected so far.

The blast damaged several buildings as far as 1 mile away, according to officials. Most of the 600 block of Heron Drive remains closed. Employees of local businesses will be allowed access, officials stated.

The cause of the explosion was not immediately known.