Gardaí have followed more than 500 lines of inquiry in relation to the explosion in Creeslough, Donegal earlier this month in which ten people died.
Gardaí said more than 260 statements have been taken, with interviews being carried out every day.
Officers have been going door-to-door since the 7 October blast at the village's service station.
A global company that specialises in the investigation and testing of energy systems, Det Norske Veritas (DNV), is on site along with crime scene managers from the Garda National Technical Bureau.
In a statement, An Garda Síochána said the preservation of the scene will be extended after the force made a further application before the High Court under Section 5 of the Criminal Justice Act 2006.
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The extension to preserve the scene up until 27 November has been granted, allowing investigators to "preserve, search for and collect evidence".
The road closure on the N56 through Creeslough will also remain in place, gardaí said, adding that it would like to thank the local community for their patience and support around the investigation.
Gardaí said a number of objects have been recovered from the scene and a number of items are being tested.
A statement from gardaí said they understand "the impact on the community and the ongoing inconvenience and disruption caused" by the investigation.
"A Memorandum of Understanding has been agreed upon and signed between An Garda Síochána, the Health and Safety Authority and the Commission for the Regulation of Utilities to facilitate the sharing of information and resources between the agencies.
"A careful and systematic approach is being taken to the forensic examination of the scene due to the structural instability of the building, which is being closely monitored by personnel on site. Structural engineers are in attendance at the site to assist in this investigation and to ensure as safe a working environment as possible," the statement continued.
An incident room is being operated out of Milford Garda Station, from where the overall investigation is being coordinated.
Gardaí added: "An Garda Síochána’s thoughts continue to be with the families of the deceased of this fatal explosion and the injured and their families.
"An Garda Síochána is working diligently and as expeditiously as possible, in the circumstances, to ensure that all the circumstances of this fatal explosion are professionally investigated."
