A trailer loaded with camels was left beside a Darling Downs highway for several hours during the weekend's heatwave, prompting a barrage of calls to police.

Concerns were raised on Saturday morning when 18 camels were left at the Charlton truck stop on the Warrego Highway outside Toowoomba's western outskirts.

The incident initially baffled police but they have now worked out what went wrong.

Senior Sergeant Trevor Stephens from the Stock Squad says

"[They] originally come over from Alice Springs and they'd been spelt in Longreach and then come from Longreach through to the Charlton yards," he said.

"They were dropped off because the road train configuration can't pull two trailers down though the main highway so one was left behind.

"There was supposed to be a second truck pick those camels up but for some reason something happened to it and it couldn't happen."

He says the animals were fine in the hot conditions, but people were worried.

Sgt Stephens says the death of one of the camels is believed to have been from natural causes and not heat-related.

The trailer containing the camels was collected around 5pm (AEST and continued on to their destination which was Caboolture.