UPDATE 1.25am Police are searching dense bush for a teenager who went missing while quadbiking in the Wheatbelt with a group yesterday morning.
The alarm was raised for the 14-year-old boy at 9.20am after he was separated from the group. He was last seen about 7.15am.
The boy was camping overnight with his father and friends in bushland off Metro Road near the Brookton Hwy.
With the temperature over 40C today, rescuers were keen to find the teenager quickly but as darkness fell they had yet to find him.
But last night, his bike was found in a big ditch about 8km south-east of the search command post.
The bike's chain was broken and the keys and the boy's helmet and gloves were missing.
The discovery allowed more than 80 State Emergency Service and local police to refine their search to a smaller area of bushland.
The police helicopter was also called in to search, using its night vision.
Search co-ordinator Ray Anderson said searchers would continue patrolling bush tracks in their vehicles throughout the night, with visibility too low for officers to search on foot.