The clean gas power company has raised $18m in debt funding in the last month and is looking to raise a series C round later this year from stategic investors.

US-based natural gas company FlexEnergy secured a further $5m in debt financing on Thursday, less than one month after it raised $13m in a similar round, and is seeking out strategic investors for a series C round later in the year through financial services firm Citigroup, according to venture capital news site VentureWire.

The latest investment was made by the Louisiana Sustainability Fund, a cleantech-focused fund operated by investment firm Sail Capital Partners. Sail, together with private equity vehicle RNS…