Maui firefighters continued to monitor the brush fire that authorities believe was deliberately set Monday, and which has scorched 5,300 acres on the southern slopes of Haleakala.

Authorities estimate that the fire is still 40 percent contained and has not spread.

However, there were multiple flare-ups that occurred Thursday. These were in pockets of unburned brush spread out within the borders of the fire. A few flared up outside the containment lines, but they were quickly doused by helicopter.

On Thursday, firefighters conducted isolated firing operations – a tactic where ground crews burn out areas of unburnt brush as a proactive measure to prevent future flare-ups. These firings were in areas where firefighters anticipate the fire posing a larger problem later. The number of bulldozers was reduced to three, as ground crews continued to establish firebreaks around problem areas.

The fire was first reported at 5:40 p.m. Monday.

Piilani Highway is currently open to traffic.

However, motorists are warned that the highway could close again at anytime without notice should flare-ups occur and it becomes necessary to use the highway for helicopter operation.