ALBANY -- The nation's health insurers are bracing for a possible legal blitz after New York Attorney General Andrew Cuomo yesterday sued industry leader UnitedHealth Group. The suit focuses mainly on United's subsidiary Ingenix, the country's largest billing-information supplier, alleging Ingenix deliberately under estimated medical costs and forced patients to over pay. Sixteen other insurers have been subpoenaed in the probe, Cuomo's announcement also stated. Cuomo's release charged that United "create[d] convoluted and dishonest systems for determining the rate of reimbursement." He added that the "lack of accuracy, transparency, and independence surrounding United's process for setting a 'reasonable and customary rate' is astounding." Amongst the 16 health insurers to receive subpoenas in the AG's billing probe are industry giants Aetna, Cigna and Empire BlueCross BlueShield. Aetna quickly released a statement yesterday evening promising to "cooperate fully in this investigation." Cuomo's release also lined up an array of support for his actions against United from groups representing consumers and physicians, including a statement from a representative of Cancer Care. The AMA's president-elect said the association "greatly appreciates the Attorney General's interest and leadership in protecting consumers." Cuomo's investigation into the health-insurance industry's billing practices has so far lasted six months. With 16 subpoenas issued, it looks like continuing for at least several more.