Engineering group AJ Lucas Group Ltd says the company has collected about $34 million from the sale of its major stake in takeover target Sydney Gas Ltd.

AJ Lucas had entered into a pre-bid agreement to sell about 59.6 million shares, or 74 per cent of the company's holding in Sydney Gas to suitor AGL Energy Ltd.

The engineering group said it had sold its remaining 20.9 million shares in Sydney Gas on-market.

Sydney Gas has recommended the all-cash takeover bid of 42.5 cents, or $171 million from AGL Energy, Australia's largest power retailer.