ROMA police are calling for information after a small bomb exploded under the bridge at Shady's Lagoon on Saturday.

The homemade explosive was detonated about 11pm on Saturday and several alarmed nearby residents called the police.

Detective Mick McGray said the blast spread over an area of 50 metres.

"No one was injured and there was no structural damage to the bridge," Detective McGray said.

But he said police were taking the matter seriously.

"We would like to remind parents to be vigilant about what their children are researching and viewing on the internet," he said.

"This device was quite a step up from a home-made smoke bomb. It involved quite thick metal containers."

Detective McGray said the consequences of unqualified people making explosives could be lethal.

If you have information, contact Roma police on 46229333 or Crime Stoppers anonymously on 1800 333 000.