Police have warned to check anything you get from a second-hand store after three children took white powder from a wallet.

The primary school aged kids were rushed to hospital after they ingested the substance they found while at a leisure centre in Footscray, Melbourne.

Police said the children were rifling through the wallet belonging to one of them when they found the powder in a small, zip lock bag about 1.40pm.

The wallet had been bought from a second-hand store some time ago.

The children were assessed at hospital and no ongoing treatment was required.

Police took no further action.

“Check whatever you buy from a second-hand shop,” a spokesman said.