Up to eight gatecrashers robbed five teens of their mobile phones at an 18th birthday party in Dandenong North.
Greater Dandenong CIU Detective Senior Constable Brendan Fontana said the gatecrashers, described as Islander in appearance, entered the Taft Close party about 9.30pm on Saturday 29 April.
One victim told police they surrounded him and demanded his watch and phone, throwing him to the ground and taking his mobile when he refused.
The thieves then fled the scene.
Det Sen Const Fontana urged anyone with information to call Crime Stoppers on 1800 333 000.
