Search continues today.
Police will today continue searching for a 24-year-old male reported missing following a camping dance party in Sydney over the weekend.
As ABC reports, police say Tiemuzhen Chalaer has not been seen since he walked into bushland at Lower Portland, Hawkesbury, to find a toilet spot sometime between 6.30am and 9am on Sunday morning.
Chalaer's friends did not realise he was missing until they returned home from the party.
"As the event has wrapped up, it's one of those situations where everyone else was assuming he was with someone else, and it was only when people returned to their homes in Sydney they realised he hadn't returned," Chief Inspector Garry Sims said.
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After Chalaer was reported missing on Sunday night, police from the Hawkesbury Local Area Command and officers from Police Rescue and PolAir began the search on Monday morning.
"We have a rescue coordinator on scene as well as police from the local area command, assisted by rural fire services, SES, public order, and also dog squad," Inspector Suzanne Rhode-Sanders said on Monday.
"And PolAir have done an extensive search over the area this morning.
"Now we're just doing a grid search of the area and hopefully we'll locate him.
"The search will continue, obviously, until it's no longer safe for our people to search and if he's not found we'll then resume the search tomorrow morning."
Police have concerns for Chalaer's welfare as he left the campsite without any supplies and reportedly suffers from a medical condition.
Police are asking anyone with information to call Crime Stoppers on 1800 333 000 or go to the Crime Stoppers website.