THE sabotage of an Ipswich tourism attraction could have had dire consequences if staff had not been vigilant, says Queensland Pioneer Steam Railway chairman Robert Shearer.

Police believe the Queensland Pioneer Steam Railway at Swanbank was broken into by two people on Thursday night shortly before 9.15pm.

Mr Shearer said it looked as though the attempted theft was an after-thought as two people spent almost 20 minutes inside a historic diesel locomotive, sabotaging the controls.

"There was evidence of tampering. They altered the directional controller so forward was back and back was forward which could have been very dangerous," he said.

"Luckily our volunteers did thorough checks and were able to rectify the problem before taking the locomotive on a public run on Sunday.

"I want to praise the train crew for being so vigilant because the situation could have easily been worse."

The QPSR chairman said the organisation bolstered security after a string of vandalism and break-in attempts last year, which led to the police being alerted so quickly. Police arrived within 10 minutes and it's a real credit to them."

QPSR volunteer Mark Griffiths also praised police for their lightning fast response.

"They tried to steal a lantern off the side of the 109-year-old PB-15 engine, as well as some copper piping and a jerry can," he said. "They also had a bag of light bulbs."

A 46-year-old Eastern Heights man was charged with entering a premises and committing an indictable offence. He also has unrelated charges of possessing dangerous drugs and failing to take reasonable care and precautions in respect of a syringe or needle.

A 36-year-old man from Flinders View was charged with one count of entering premises and committing an indictable offence and an unrelated charge of failing to take reasonable care and precautions in respect of syringe or needle.

Both men will appear in Ipswich Magistrates Court on May 2.