THREE youths are in police custody after a suspicious fire in Sydney's west.
Firefighters have contained the blaze in Shalvey, near Blacktown, which affected about 10ha of bushland today, a Rural Fire Service (RFS) spokesman said.
The three youths were taken into custody this afternoon and are helping police with their inquiries.
Deputy police commissioner Mick Fuller warned that police and fire authorities have the technology to quickly find arsonists.
"The RFS are using aerial technology to examine fires as they occur," Mr Fuller said.
"This helps the RFS and Arson Unit investigators determine if the fire is suspicious.
"If it is found to be suspicious local police and arson investigators are sent to the scene.
"As a result of using this strategy three people are currently in custody, assisting police with inquiries."
The spokesman said authorities suspect it was deliberately lit because it sparked from multiple ignition points.
Emergency services were called to Shalvey at about 1.15pm today following reports of a fire.
About 15 RFS fire trucks battled the blaze, which was eventually brought under control after two and a half hours.