Police have raided a house and seized shoes and a cellphone as they close in on teenagers involved in the 'drown him' assault case.

Four teenagers attacked a 15-year-old, dragged him to a water race and held his head underwater chanting "drown him."

The incident took place in Rolleston on November 4 after a fireworks display.

The victim spent the night in hospital because of his injuries.

Police have been tight-lipped over their investigation since the attack was revealed last month.

But yesterday they confirmed a search warrant was executed on a Rolleston property last week.

"Police have executed a search warrant in regard to this matter as we continue to gather evidence," a spokeswoman said.

"Police have identified people of interest and no one else is being sought. Police are continuing to support the victim."

The Star has learned shoes and a cellphone were seized.

But police would not discuss any specifics of what was taken in the raid.

The teenager was assaulted when he allegedly refused to hand over his cap after he was confronted by four other teenagers on Tennyson St at about 10.30pm on November 4.