A former US Customs and Border Protection Commissioner says human trafficking's become financially lucrative to people smugglers.

It follows the deaths of 50 migrants inside a Texas truck.

They were discovered inside a trailer unit yesterday in San Antonio, with temperatures nearing 40 degrees Celsius.

There were no signs of water or working air conditioning.

Gil Kerklikowske told Kate Hawkesby there have been warnings for decades about the dangers they face.

He says despite that, many still attempt the crossing for either safety or a better life.

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