Origin Energy (ASX: ORG) said potentially toxic chemicals discovered in coal seam wells pose no major health risk after tests of water from its Australia Pacific LNG coal seam gas fields.

The company said in a statement on Friday an investigation into traces of BTEX chemicals - benzene, toluene, ethylbenzene and xylene found in water from exploration activities in October found there was no significant risk to the environment or human health.

It added Australia Pacific LNG has kept the Queensland Government fully informed of the investigation, providing detailed information to the Queensland regulator, the Department of Environment and Resource Management (DERM).

DERM has confirmed the company's proposed monitoring and reporting guidelines to manage Hydraulic Fracture Stimulation (HFS) programs are appropriate.

The investigation identified possible sources of BTEX contaminants, including small amounts of lubricants and diesel which may have been introduced inadvertently in the course of operations. Processed mineral oil present in an additive previously used in HFS fluids was also identified as containing trace levels of TEX chemicals (well below Australian Drinking Water Guidelines).

Origin said, "These potential sources are being addressed with strengthened control measures put in place for future HFS operations in collaboration with HFS service providers.

"Steps have been and will continue to be taken to ensure that all HFS fluids meet laws passed by Queensland Parliament on 23 November 2010."

According to Origin, the investigation has also indicated that trace levels of BTEX may be naturally occurring under certain conditions and operations will be conducted in a manner that manages environmental risk and protects water sources both at the surface and below the ground.

"Australia Pacific LNG already has strict controls in place to ensure that water produced from wells is contained in lined and fenced ponds and tanks ahead of treatment as part of its current operational practice," it said.

"This ensures that produced water is isolated from water courses and livestock during its treatment."

Following the investigation and the implementation of additional controls and assurance processes, Australia Pacific LNG will recommence HFS operations.

"Australia Pacific LNG will continue regular testing of water from its operations and reporting of results to DERM and is committed to meeting its monitoring and reporting obligations to DERM," said Origin.